fix(server): children start in full access; drop agent- and kit-set runtimeMode

[lukemaj]

What: child threads always start in full-access; spawn_thread no longer takes runtimeMode, and the Prism role kit no longer has one.
Why: a child's approvals go only to the user and the planner cannot see or answer them, so a restricted child stalls unseen; copying the parent's mode would also make a read-only dispatcher's implementers read-only.
So what: ready for review; merging needs the user's approval.

Closes #88

Change

• threads/tools.ts: removed runtimeMode from SpawnThreadInput; the role description no longer promises per-role permissions.
• threads/handlers.ts: a child is created with DEFAULT_RUNTIME_MODE instead of kit ?? parent.
• contracts/prism.ts: removed runtimeMode from role kits and kit patches. Saved settings carrying it still decode (the key is dropped).
• Tests: the schema omits runtimeMode and a passed value is dropped (roles.test.ts); the child of an approval-required parent starts in full-access (childReportState.test.ts); old saved settings load (prism.test.ts).

Proof

• vp test run src/mcp/toolkits/threads (apps/server): 41 passed.
• vp test run src/prism.test.ts (packages/contracts): 9 passed.
• tsc --noEmit apps/server and packages/contracts: exit 0.
• Against the old code: the schema test fails (1 failed / 17 passed), and the child-mode test fails with expected 'approval-required' to be 'full-access'.

Elon record

• Requirements and who asked: the user wants children never blocked on approvals they did not request, and implementers not limited by a restricted dispatcher; nobody asked for agents or kits to pick a child's mode.
• Deleted: spawn_thread.runtimeMode, the role-kit runtimeMode (unused in the user's settings), and parent-mode inheritance for children.
• Bottleneck: child approvals route only to the user, invisible to the planner.
• Checked myself: handlers.ts was the only reader; no web or mobile code shows the kit field; the user's settings set no role mode; the thread toolkit has no approval tool or waiting-for-approval status.

Done by Claude Opus 5.5 in Claude Code (T3 Code).

🤖 Generated with Claude Code

[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	13.5 KiB	13.5 KiB	+36 B (+0.3%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	+2 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.4 KiB	6.4 KiB	+34 B (+0.5%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.2 KiB	56.2 KiB	+44 B (+0.1%)	66.4 KiB	✅
Codex	Live turn messages	8	9	+1 (+12.5%)	21	✅
Claude	Total thread wire	13.5 KiB	13.5 KiB	+2 B (+0.0%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	+3 B (+0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.5 KiB	6.4 KiB	−1 B (−0.0%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.0 KiB	57.0 KiB	0 B (0.0%)	66.4 KiB	✅
Claude	Live turn messages	9	9	0 (0.0%)	21	✅

Baseline: c0132ad · PR result: e1a54cd · 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: 113.9 KiB
• Claude decoded thread snapshot: 114.6 KiB

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