docs(agents): bring agent-facing docs in line with the R44 fix

Six docs lagged after the post-merge R44 fix added withCapture +
reported-flag.ts. They mentioned withSpan only and described the
capture story as if it were inline in use-case / controller bodies.
This commit aligns them with what shipped.

CLAUDE.md (Key Conventions):
- "Spans applied at DI bind time" → "Spans + capture composed at DI
  bind time" with the withSpan(withCapture(factory)) sandwich and the
  outermost-span ordering note.
- "Capture at throw sites only" expanded to mention the
  __sentryReported flag, the three flag-checking sites (withCapture,
  SentryLogger, RecordingLogger), and where the helper lives.

AGENTS.md (Instrumentation conventions):
- Use case + controller wrapping example shows the full sandwich.
- Capture-rules table now explicitly says "via withCapture" for use
  cases and controllers, and "flag set, withCapture bails" for the
  bubbled cases.

packages/core-shared/AGENTS.md:
- "with-span.ts" entry split into a paired with-span + with-capture
  block, including the actual sandwich code.
- New entry for reported-flag.ts explaining the helper and why
  RecordingLogger inlines the check (boundary rule).
- Barrel re-export list updated.

docs/architecture/vertical-feature-spec.md (§16):
- The bind-production line now describes the withSpan(withCapture(...))
  sandwich, the outermost-span rationale, and the bubbled-error bail.

docs/architecture/dependency-flow.md (TRACER/LOGGER subsection):
- bindAll diagram updated: real repo line annotates inline calls; use
  case + controller lines show withSpan(withCapture(...)).

docs/guides/tdd-workflow.md (Asserting spans and captures):
- Direct-injection example shows the binder sandwich.
- Capture-assertion example explains the flag-bail behaviour and
  links to the new tests/r44-no-double-capture.test.ts e2e example.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -385,28 +385,38 @@ return this.tracer.startSpan(
 );
 ```
 
-**Use case + controller spans (applied at DI bind time):**
+**Use case + controller spans + capture (applied at DI bind time):**
 
 ```ts
 const wrappedUC = withSpan(
   tracer,
   { name: "blog.getArticles", op: "use-case" },
-  getArticlesUseCase(repo),
+  withCapture(
+    logger,
+    { feature: "blog", layer: "use-case", name: "blog.getArticles" },
+    getArticlesUseCase(repo),
+  ),
 );
 const wrappedCtrl = withSpan(
   tracer,
   { name: "blog.getArticles", op: "controller" },
-  getArticlesController(wrappedUC),
+  withCapture(
+    logger,
+    { feature: "blog", layer: "controller", name: "blog.getArticles" },
+    getArticlesController(wrappedUC),
+  ),
 );
 ```
 
-**Capture rules:**
+`withSpan` is outermost; `withCapture` is between span and factory so the error is captured before the span closes with error status. Bodies stay vendor-clean — neither use cases nor controllers call `tracer` / `logger` inline.
+
+**Capture rules** (each error captured exactly once via the `__sentryReported` flag from `core-shared/instrumentation/reported-flag.ts`):
 
 | Layer | Captures | Doesn't capture |
 |---|---|---|
-| Repository | Infra/Payload errors that originate here | Bubbled errors |
-| Use case | Business-rule violations originated in this body | Errors from repos (already captured) |
-| Controller | `InputParseError` from safeParse failure | Anything else |
+| Repository | Infra/Payload errors that originate here (inline in catch) | Bubbled errors |
+| Use case | Business-rule violations + output-schema failures originated in this body (via `withCapture`) | Errors from repos — flag set, `withCapture` bails |
+| Controller | `InputParseError` from `safeParse` failure (via `withCapture`) | Errors from use cases — flag set, `withCapture` bails |
 | `defineErrorMiddleware` | Nothing — maps domain → TRPCError only | — |
 
 **Boundary rule (eslint-enforced, R40):**