Align PlanAnvil with Codex CLI 0.152 runtime contracts

[KeyffMS]

Summary

Aligns PlanAnvil product semantics and live qualification with the actual Codex CLI 0.152.x implementation rather than weakening tests around observed failures.

Product changes

• add an explicit Codex 0.152 runtime contract;
• require exact agent_type for PlanAnvil profiler/reviewer children so SubagentStart matchers receive the intended role;
• treat PreToolUse as an early guard, not the sole mutation boundary;
• require an immediate deterministic Git/filesystem postcondition after direct file-changing tool calls;
• promote the generated plan/golden execution contract to PlanAnvil 2.3 with flat direct-child topology, exact roles, retry model, approvals, mutation postconditions, and compaction semantics.

Qualification alignment

• C06 exercises the Codex 0.152 guaranteed exec_command -> canonical Bash PreToolUse adapter and separately proves the product's deterministic postcondition on a direct file-change path;
• C08/C09 disable TokenBudget only inside the disposable qualification fixture so the intentionally-low auto-compaction limit is the effective trigger instead of being raised by the fallback buffer;
• C13 explicitly spawns fixture_agent with agent_type=fixture_agent and treats continue=false according to Codex 0.152 semantics;
• C03 uses the regenerated 2.3 golden plan;
• C16 retains the already-reproduced deterministic outer diagnostic path.

Safety

No approval/sandbox bypass, privileged execution, network expansion, or weakening of source/worktree invariants. Normal product configuration does not disable user TokenBudget; that override exists only in isolated live-qualification fixtures.