eval: prove stable agent identity and presentation metadata

[schickling-assistant]

Summary

• specify stable Agent Spec identity separately from optional mutable name and description
• add model-free contract coverage for exact-ID routing, constrained source-preserving authoring, duplicate names, atomic PTY projection, idempotence, and lifecycle control
• add continuity coverage proving presentation-only edits preserve the live process and durable inbox, context, decisions, resources, presence, and transcript
• pin the corpus to the exact st2 source, source archive, and reproducible Nix binary

Evidence for compoundingtech/st2#128.

Upstream dependencies:

• Separate stable agent identity from mutable presentation st2#133 at acb00164d8e1d0b08e70c8cc7fb932aee214f555
• Patch session metadata atomically by stable ID pty#142 at 4c67fb51a161b66e949b5be905ca9164f7a04c99
• Allow duplicate display names with unambiguous resolution pty#139 prerequisite at 582519fd5dd402f4d3bb9ce082292859213c6c90

Verification

Using st2 acb00164d8e1d0b08e70c8cc7fb932aee214f555 and PTY 4c67fb51a161b66e949b5be905ca9164f7a04c99:

• agent-presentation-contract: 9 PASS / 0 FAIL / 9 gating judges
• agent-presentation-continuity: 6 PASS / 0 FAIL / 6 gating judges
• reproducible st2 binary SHA256: bd933332784b1d87ba3d539c5570e4e3fd0572504ee2ec1ee52acbb5e8cdbbf4
• source archive SHA256: c09a743c5a757998edcb3ff2963b80e459a9050d8c452d5eb3b241d34806ac86

The current-main corpus gate passed provenance, 172 shell parses, policy/history/event-first checks, 84 KDL parses, semantic loading of 49 evals and strict validation of 12 nested catalogs, all fixture-reset checks, harness coverage, VRS scope-drift, and VRS variation checks. It then stopped only because the host-global commit policy rejected the synthetic worktree-actor@eval.invalid identity used by check-weird-git-setup.sh. The guard was not bypassed. The remaining independent checks all pass: preflight closed-set mutations, overnight policy, no-PII, no-PII history, generated catalog, and git diff --check.

[schickling-assistant]

Superseded by #70, which rebases the acceptance contract onto current main and verifies the final st2#136 candidate at dcf77b758adc5d6260af5f55781745a2a758bcce with PTY 706e4f5e4cd88fe24ce5b8afb7dbd507bd3e215c.