docs(spec): fix the L3 Connector example in SYNC_ARCHITECTURE.md and gate it (#5515) (#5603)

The `sapConnector` example taught four spellings `integration/connector.zod.ts`
turns down. Measured with the compiler API before the fix, verbatim:

  TS2353  'sourceField' does not exist in '{ source: string; target: string; ... }'
  TS2322  '"custom"' is not assignable to
          '"map" | "lookup" | "constant" | "cast" | "javascript"'
  TS2353  'retryPolicy' does not exist in the webhook shape
  TS2322  'string' is not assignable to '{ dialect: "cel"|"cron"|"template"; ... }'

Fixed in the document:

  - fieldMappings[].sourceField/targetField -> source/target, the canonical
    spelling of the base protocol in shared/mapping.zod.ts.
  - transform { type: 'custom', function } -> { type: 'javascript', expression },
    the nearest real member of the five-way discriminated union. The bare
    string is ExpressionInput shorthand and parses to { dialect, source }.
  - webhooks[].retryPolicy removed. WebhookSchema is a strictObject and
    already carries a curated tombstone for it (#3494): delivery retries are
    owned by the messaging outbox on a fixed schedule. There is no equivalent
    key, so the block becomes a comment saying why -- and saying that the
    sibling `retryConfig` is a different thing (the connector's own calls).
  - the annotation is now ConnectorInput (z.input), which is what an author
    writes. The bare `Connector` is z.infer on this file, so it is the shape a
    parse RETURNS. Flipping this file's 20 aliases to the #4963 X / XParsed
    house convention is a real but separate appetite -- filed as #5551 -- and
    is deliberately NOT done here.

New gate: packages/spec/src/integration/connector-author-shape.test.ts, a
sibling of automation/etl-author-shape.test.ts (#4963 / PR #5514) owned by the
schema that owns the example. It compiles the L3 block verbatim, import line
included, with a harness self-test against vacuity; classifies the document's
three `Connector` blocks (two Migration-Guide sketches elide with a bare `...`
and are not TypeScript); restores each of the four defects as a probe that must
go red with a named diagnostic; and pins what the schema SAYS at runtime for
each -- a curated tombstone for `retryPolicy`, a silent strip plus missing
`source`/`target` for `sourceField` (the curated alias for that word lives on
./data's ImportFieldMappingSchema, not this one), a value verdict naming the
five members for 'custom'.

The document's total ```typescript block count is unchanged at 6; the sibling
gate's pin holds.

Fixes #5515


Claude-Session: https://claude.ai/code/session_018fxLGQdatPbBUvCgiVxg6D

Co-authored-by: Claude <noreply@anthropic.com>

Author: os-zhuang

packages/spec/docs/SYNC_ARCHITECTURE.md

@@ -210,10 +210,29 @@ Complete, production-grade integration with external systems. Includes authentic
 
 ### Example
 
+> **`ConnectorInput` is the AUTHOR shape.** It is `z.input` of
+> `ConnectorSchema`, so every key carrying a `.default()` — `enabled`,
+> `status`, `connectionTimeoutMs`, `requestTimeoutMs`, all of `syncConfig`'s
+> `strategy` / `direction` / `realtimeSync` / `conflictResolution` /
+> `batchSize` / `deleteMode`, a mapping's `required` / `syncMode`, a webhook's
+> `method` / `timeoutMs` / `isActive` / `signatureAlgorithm` — is optional when
+> you write a connector, and `syncConfig.schedule` takes the bare cron string
+> the schema wraps for you. Annotate the **result** of
+> `ConnectorSchema.parse(…)` with the bare **`Connector`**, which is `z.infer`:
+> there those keys are all present and `schedule` is already the
+> `{ dialect: 'cron', source }` envelope. Note the asymmetry with L2 above,
+> where the bare `ETLPipeline` *is* the author shape and the parse result is
+> `ETLPipelineParsed` — `integration/connector.zod.ts` has not been moved onto
+> that house convention yet (#5551). The example below states the defaulted
+> keys anyway, because it is a tour of the surface; the Migration Guide's
+> sketches omit them, because that is what ordinary authoring looks like.
+> To have the literal validated as you write it, prefer `defineConnector(…)`,
+> which takes this same input shape and returns the parsed one.
+
 ```typescript
-import { Connector } from '@objectstack/spec/integration';
+import type { ConnectorInput } from '@objectstack/spec/integration';
 
-const sapConnector: Connector = {
+const sapConnector: ConnectorInput = {
   name: 'sap_erp_connector',
   label: 'SAP ERP Integration',
   type: 'saas',
@@ -241,22 +260,28 @@ const sapConnector: Connector = {
     deleteMode: 'soft_delete'
   },
 
-  // Field Mappings with Transformations
+  // Field Mappings with Transformations.
+  // The keys are `source` / `target` — the canonical spelling of the base
+  // protocol in `shared/mapping.zod.ts`, which every mapping surface extends.
   fieldMappings: [
     {
-      sourceField: 'customer_number',
-      targetField: 'customer_id',
+      source: 'customer_number',
+      target: 'customer_id',
       dataType: 'string',
       required: true,
       syncMode: 'bidirectional'
     },
     {
-      sourceField: 'order_value',
-      targetField: 'order_total',
+      source: 'order_value',
+      target: 'order_total',
       dataType: 'number',
+      // `transform.type` is a discriminated union with exactly five members:
+      // `constant` / `cast` / `lookup` / `javascript` / `map`. The bare string
+      // below is `ExpressionInput` shorthand — the schema wraps it into an
+      // `{ dialect, source }` envelope on parse.
       transform: {
-        type: 'custom',
-        function: 'value => parseFloat(value) / 100' // Convert cents to dollars
+        type: 'javascript',
+        expression: 'value / 100' // Convert cents to dollars
       },
       syncMode: 'bidirectional'
     }
@@ -270,11 +295,11 @@ const sapConnector: Connector = {
       events: ['record.created', 'record.updated'],
       secret: process.env.WEBHOOK_SECRET!,
       signatureAlgorithm: 'hmac_sha256',
-      retryPolicy: {
-        maxRetries: 3,
-        backoffStrategy: 'exponential',
-        initialDelayMs: 1000
-      },
+      // (`retryPolicy` sat here until #3494 retired it — webhook delivery
+      // retries are owned by the messaging outbox on a fixed schedule, and the
+      // authored policy was never read. There is no replacement, and it is a
+      // different thing from `retryConfig` below, which governs the calls this
+      // connector MAKES.)
       timeoutMs: 30000,
       isActive: true
     }
@@ -283,7 +308,7 @@ const sapConnector: Connector = {
   // (`rateLimitConfig` sat here until #4911 retired it — no outbound
   // rate-limiting engine ever existed. Throttle at the provider/gateway.)
 
-  // Retry Configuration
+  // Retry Configuration — for the connector's own outbound requests
   retryConfig: {
     strategy: 'exponential_backoff',
     maxAttempts: 5,
@@ -378,7 +403,7 @@ When a connector's declarative sync needs complex transformations:
 
 **Before (L3 `syncConfig`):**
 ```typescript
-const connector: Connector = {
+const connector: ConnectorInput = {
   name: 'orders',
   type: 'saas',
   authentication: { type: 'api-key', ... },
@@ -423,7 +448,7 @@ const pipeline: ETLPipeline = {
 
 **After (L3):**
 ```typescript
-const connector: Connector = {
+const connector: ConnectorInput = {
   authentication: { type: 'oauth2', ... },
   webhooks: [...],
   retryConfig: { ... }

packages/spec/src/automation/etl-author-shape.test.ts

@@ -113,15 +113,17 @@ describe('[#4963] SYNC_ARCHITECTURE.md pipeline examples compile', () => {
     // assertion below pass over an empty program — the way a gate goes dormant.
     expect(pipelineBlocks.length, 'ETLPipeline examples in SYNC_ARCHITECTURE.md').toBe(3);
     // The other three are the L3 `Connector` examples, out of this gate's scope
-    // because they belong to `integration/connector.zod.ts`. Two of them are
-    // Migration-Guide sketches that elide with a bare `...`, which is not
-    // TypeScript. The third — the full `sapConnector` example — is NOT exempt on
-    // its merits: run through this same harness it reports four diagnostics, and
-    // three of them are keys or values the schema REJECTS (`sourceField` /
-    // `targetField` for `source` / `target`, `transform.type: 'custom'`,
-    // `webhooks[].retryPolicy`). That is filed as #5515, not fixed here, because
-    // the fourth diagnostic is `Connector` being `z.infer` — this issue's twin
-    // on a file whose migration surface is NOT empty, so it needs its own ruling.
+    // because they belong to `integration/connector.zod.ts` — and covered, since
+    // #5515, by that file's own gate: `integration/connector-author-shape.test.ts`
+    // classifies the same three (two Migration-Guide sketches that elide with a
+    // bare `...`, which is not TypeScript; one full `sapConnector` example) and
+    // compiles the third. When this pin was written that example reported four
+    // diagnostics, three of them keys or values the schema REJECTS (`sourceField`
+    // / `targetField` for `source` / `target`, `transform.type: 'custom'`,
+    // `webhooks[].retryPolicy`); those are fixed in the document. The fourth was
+    // `Connector` being `z.infer` — this issue's twin on a file whose migration
+    // surface is NOT empty — and it is solved there by annotating the example
+    // with `ConnectorInput`; the alias flip itself is still open as #5551.
     // The total is pinned rather than left open so that ADDING a block to this
     // document is a decision someone has to make on purpose: a new ETL example
     // is picked up automatically by the selector above, and anything else