#270)

## Related work

Parent ticket: AGX1-242 - AgentEx authorization dual-write.

This change is part of a 4-PR stack across 3 repos.

| Repo | PR | Purpose |
|---|---|---|
| scaleapi/scaleapi |
[scaleapi/scaleapi#146335](scaleapi/scaleapi#146335)
| merged flag registry update for the shared AgentEx resources rollout
flags |
| scaleapi/agentex |
[scaleapi/agentex#364](scaleapi/agentex#364) |
agentex-auth routes each auth verb to one backend target |
| **scaleapi/scale-agentex** | **this PR** | **registers agentex
resources in the authorization graph and grants agent/task ownership** |
| scaleapi/scale-agentex |
[#271](#271)
| denied direct agent access collapses to 404 |

**Merge/deploy order:**
[scaleapi/scaleapi#146335](scaleapi/scaleapi#146335)
is merged; deploy
[scaleapi/agentex#364](scaleapi/agentex#364)
before this PR, then merge/deploy
[#271](#271).
Rollout per account is: enable `fgac-agentex-resources-dual-write`,
backfill existing resources into Spark, then enable
`fgac-agentex-resources` reads.

## What

Registers agentex resources in the authorization graph on create and
removes them on delete, separating resource lifecycle from explicit
ownership:

- **Agents and tasks** register in the authorization graph on create and
record an explicit owner; on delete they deregister and the owner record
is revoked.
- **Schedules and agent API keys** register under their parent agent on
create and deregister on delete. Permissions cascade from the parent
agent, so no separate owner record is written.

Registration runs before the resource is persisted, so an authorization
failure fails closed with no orphaned row. If the persist (or the
Temporal create, for schedules) later fails, a compensating deregister
runs.

## Why

Giving each verb a single backend keeps the existing ownership writes
(`grant`/`revoke`) unchanged and confines the new behavior to the new
lifecycle interface (`register`/`deregister`). Explicit ownership is
recorded only for agents and tasks; schedules and agent API keys inherit
access from their parent agent, so they need no owner record of their
own. Issuing the two write kinds independently keeps both backends
current, so reads can cut over per account with a clean rollback.

## Testing

- Unit and integration tests covering the agent, task, schedule, and
api_key authorization writes (register/deregister ordering,
fail-closed-before-persist, and compensating cleanup).
- `ruff check` / `ruff format`.

#271 made denied agent-route access collapse to 404 instead of 403 and
updated the unit authz tests, but this events integration test still
asserted 403 -- leaving it red on main and on any open PR. Align the
expectation and name with the 404 convention. CI confirms the events
route already returns 404 for a denied agent (the assertion failed with
`404 == 403`); this only updates the test to match the intended behavior.

Resource ownership was not recorded on agentex resource creation under
fine-grained access control, due to two independent bugs.

Changes:
- is_whitelisted_route: use a boundary-aware match (the route itself or
  a true sub-path) so /agents/register-build authenticates and carries
  the caller principal, instead of being swept in by the
  /agents/register prefix.
- Resolve the creator from the dict principal context in the agent,
  agent_api_key, and schedule register helpers; getattr on the untyped
  dict always returned None and silently skipped registration.
- Update the events authz test to expect 404 for denied agent-route
  access, per the collapse-to-404 convention (#271).