fix(delegation): observe completed children as completed and suppress bookkeeping rows

[rynfar]

Problem

Delegated children whose turns complete before a server restart or the idle reaper were being observed as interrupted by DelegationFollowThroughReactor because observeDelegatedChild prioritized a stopped session status over terminal turn states. In addition, changed child observations at startup could trigger stale wake turns, and internal delegation bookkeeping activity rows (delegation.child-state and delegation.follow-through.delivered) were rendering as clutter in web and mobile work logs.

What changed

• Task 1: Reordered state precedence in observeDelegatedChild (apps/server/src/orchestration/delegationFollowThrough.logic.ts) so terminal turn states (completed, interrupted, error) take precedence over a session stopped afterwards by a restart or the idle reaper, matching deriveDelegatedThreadState.
• Task 2: Updated DelegationFollowThroughReactor.ts to baseline any child observation whose notice key changed while the server was down (startupPass && work.liveChildId !== child.id), preventing historical turns from triggering stale wakes.
• Task 3: Added delegation.child-state and delegation.follow-through.delivered to the web work log skip list in apps/web/src/session-logic.ts, keeping reactor bookkeeping hidden while leaving the user-facing delegation.follow-through.paused notice visible.
• Task 4: Added the same bookkeeping activity kinds to the mobile feed skip list in apps/mobile/src/lib/threadActivity.ts.
• Task 5: Documented accurate delegation boundaries and observation precedence in docs/internals/delegation.md, and appended durable fact 2026-09-18-delegation-follow-through-observation to .agents/durable-facts.jsonl.

Verification

• vp test run apps/server/src/orchestration/delegationFollowThrough.logic.test.ts: PASS (13 passed)
• vp test run apps/server/src/orchestration/DelegationFollowThroughReactor.test.ts: PASS (15 passed)
• vp run -F t3 typecheck: PASS (exit 0)
• vp test run apps/web/src/session-logic.test.ts: PASS (95 passed)
• vp run -F @t3tools/web typecheck: PASS (exit 0)
• vp test run apps/mobile/src/lib/threadActivity.test.ts: PASS (112 passed)
• vp run -F @t3tools/mobile typecheck: PASS (exit 0)
• vp fmt --check <modified files>: PASS (correct format)
• vp lint <modified code files>: PASS (0 errors, 0 warnings)
• Guard-rail diff check against origin/pylon for prohibited files: PASS (empty diff)

Not covered

No live provider runs; PR #620 files untouched.

Part of #622.

Planned and verified by Claude Fable 5.1 in Claude Code; implemented by Gemini 3.8 Flash (High) in Antigravity, as a Pylon delegated child.

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Project	Deployment	Actions	Updated
pylon-marketing	Ready	Preview	Sep 18, 2026 5:18am UTC

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	14.0 KiB	14.0 KiB	+14 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.2 KiB	7.2 KiB	−7 B (−0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.7 KiB	6.7 KiB	+21 B (+0.3%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.0 KiB	58.0 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	9	9	0 (0.0%)	21	✅
Claude	Total thread wire	14.0 KiB	14.0 KiB	−4 B (−0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.2 KiB	7.2 KiB	+11 B (+0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.8 KiB	6.7 KiB	−15 B (−0.2%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.9 KiB	58.9 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: a85762e · PR result: 6400031 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 115.7 KiB
• Claude decoded thread snapshot: 116.4 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.