fix: unblock workspace build (bot session result typing + bots/signal tests)

[NecatiY]

Summary

The workspace build (pnpm -r build → tsc -p tsconfig.json) fails on three packages. This PR fixes all of them — verified: 712 test files / 3522 tests pass, and every package in the workspace builds clean.

Bugs fixed

1. packages/bot/core + packages/bots/core — TS2345 build break

Both trees (the duplicate in bot/ and the maintained bots/) fail to compile:

src/index.ts(126,19): error TS2345: Argument of type '{ type: string; ... }' is not assignable
to parameter of type 'AIResult'. Types of property 'type' are incompatible.
Type 'string' is not assignable to type '"result"'.

The finish() callback parameter was typed as a loose object shape instead of AIResult. Fixed by typing it (result: AIResult). This also resolves the exact failure mode described in #942/#943 — the stale bot/ copy still breaks the build, and so does bots/.

2. packages/bots/signal — test file does not compile

src/index.test.ts fails typecheck:

• groupId: undefined is not assignable to string | null → widened the IncomingMessage.groupId field to string | null | undefined. The implementation already falls back via msg.groupId ?? msg.source, so undefined is a valid runtime input.
• the test literal passed an undeclared raw field (unused anywhere in the implementation) and omitted required isGroup → cleaned up the literal.

Verification

• tsc -p tsconfig.json exit 0 on every package (top-level + nested) in the workspace
• vitest run: 712 files passed, 3522 tests passed, 1 skipped

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[github-actions]

🤖 Auto-rebase: The branch was rebased successfully locally but could not be pushed to the fork. Please enable 'Allow edits from maintainers' in the PR settings, or rebase manually: git fetch upstream master && git rebase upstream/master.

[NecatiY]

Closing in favour of #942, which landed the same TS2345 build fix (bot/bots core) on 2026-08-09. My branch had also gone dirty and I don't want to浪费 a maintainer rebase on a now-redundant change.

Instead I opened #948 — the Telegram integration was the only remaining packages/bots/* bot whose toBotEvent still used the unsafe new Date(msg.timestamp).toISOString(), so I applied the same guard discord (#933) and signal (#932) already have. 16 tests pass locally.