feat(observability): anchor native time to first token at the accepted wake (#19838)

## Thinking Path

> - Paperclip is the open source app people use to manage AI agents for
work
> - When someone messages an agent, the reply must start fast. The
durable ownership plan (#19831) makes time to first token (TTFT) a hard
invariant.
> - Phase 0 of that plan records a TTFT baseline per adapter and
environment, measured from the moment the message or wake is accepted.
> - Today `task.time_to_first_token` starts at the wake comment, the
answered question, or the run row's creation. A wake request that was
accepted earlier (deferred, coalesced or retried) is not part of the
measurement, and the span does not say which start it used.
> - This pull request moves the start back to the earliest accepted
input and names it on the span.
> - The benefit is that the baseline and later budgets measure what the
user waits for, with no new work before `turn.start`.

## Linked Issues or Issue Description

Refs #19831

**What is the problem?**
`task.time_to_first_token` does not include the time between an accepted
wake request and the creation of its run row. It also does not record
which input it started from.

**What is the expected outcome?**
The span starts at the earliest accepted input and carries an `anchor`
attribute: `comment`, `question_response`, `wake_request` or
`run_created`.

**Why does it matter?**
Phase 0 of the durable ownership plan sets TTFT budgets from this
baseline. A start that skips queue time hides the latency that deferred
wakes add.

## What Changed

- `resolveNativeTimeToFirstTokenStart` (pure) in `native-run-trace.ts`
picks the start and the anchor. `anchor` joins the closed span-attribute
allowlist.
- `readNativeRunWakeRequestedAtMs` reads
`agent_wakeup_requests.requested_at` for the run. It never throws.
- `native-session-executor.ts` calls it only after the first deliverable
text, so it adds no wait before `turn.start`. The span now ends at the
text commit time, not after the trace write.
- Updated `doc/run-log-events.md` and `doc/observability.md`.

## Verification

- `cd server && npx vitest run
src/services/native-runtime/native-run-trace.test.ts
src/services/native-runtime/native-run-wake-anchor.test.ts` (26 pass).
- `cd server && npx vitest run
src/services/native-runtime/native-session-executor.test.ts -t first`
(41 pass). The existing TTFT test now asserts the anchor for each
ingress.

## Risks

- Low risk. This changes only the run-log and OTLP span. It is not
Telemetry (AGENTS.md §5.7), and it does not change runtime behavior.
- One indexed primary-key read per native dispatch, after the first
text. A read failure drops the anchor and keeps the old start.
- TTFT values can grow for deferred wakes. That is the intended
correction. `startOffsetMs` can be negative when the wake request comes
before the trace start.

## Model Used

- Claude Opus 5.5 (`claude-opus-5-5`), via Claude Code with tool use and
code execution.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [ ] I will address all Greptile and reviewer comments before
requesting merge

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

server/src/services/native-runtime/native-session-executor.ts

@@ -284,11 +284,13 @@ import {
   isNativeRunRootHistoricalSpan,
   nativeRunPreparationStarts,
   recordNativeProviderPerformanceSpans,
+  resolveNativeTimeToFirstTokenStart,
   type NativeRunHistoricalSpan,
   type NativeRunSpanScope,
   type NativeRunTrace,
 } from "./native-run-trace.js";
 import { createNativeHarnessBackupStamp } from "./native-harness-backup-stamp.js";
+import { readNativeRunWakeRequestedAtMs } from "./native-run-wake-anchor.js";
 import { noteNativeRunnerEvidence } from "./native-runner-evidence-signal.js";
 import { removeNativeHarnessBackup } from "./native-harness-backup-cleanup.js";
 import { registerLiveRunnerGoalController } from "../runner-goal-control-broker.js";
@@ -10206,12 +10208,21 @@ async function executePaperclipNativeSessionWithinScope(
           firstTokenRecorded = true;
           const textAt = Date.now();
           await trace.record({name:"response.first_nonempty_text",parentName:"native.session.execute",startedAtMs:textAt,endedAtMs:textAt});
-          await trace.record({
-            name: "task.time_to_first_token",
-            parentName: "task.provider_session",
-            startedAtMs: trace.traceStartedAtMs,
-            endedAtMs: Date.now(),
-            attributes: { eventKind: textKind },
+          // Detached: the anchor read never delays this event, later events,
+          // or turn.start (invariant 8). The trace settles it at finish.
+          trace.defer(async () => {
+            const ttftStart = resolveNativeTimeToFirstTokenStart({
+              traceStartedAtMs: trace.traceStartedAtMs,
+              preparationSpans,
+              wakeRequestedAtMs: await readNativeRunWakeRequestedAtMs(input.db, input.execution.binding.runId),
+            });
+            await trace.record({
+              name: "task.time_to_first_token",
+              parentName: "task.provider_session",
+              startedAtMs: ttftStart.startedAtMs,
+              endedAtMs: textAt,
+              attributes: { eventKind: textKind, anchor: ttftStart.anchor },
+            });
           });
         }
         await observeAccountingEvent(event);