feat(context): add evidence-aware execution and runtime contracts

[tcconnally]

Summary

This PR resolves the four linked context/runtime issues as one compatible contract wave:

• Adds a canonical capability evidence matrix with claim ceilings and generated public surfaces.
• Adds versioned resource-aware execution profiles with deterministic resolution, hard context limits, and degraded-plan diagnostics.
• Adds a portable, digest-only runtime adapter seam with sanitized capability/request/result envelopes and an offline reference adapter.
• Adds deterministic evidence/uncertainty/abstention projections to compiled context contracts.

The implementation remains provider-neutral: Vault remains the memory/retrieval authority, Ledger remains the evidence/provenance authority, and Perseus only consumes normalized references and commitments. No credentials, raw prompts, private memory bodies, inference engine, vendor accelerator, or neuromorphic implementation is introduced.

Verification

• python3 scripts/build.py --check
• python3 scripts/render_claims.py --check
• ./.venv/bin/python -m pytest tests/ -q — 2464 passed, 6 skipped
• git diff --cached --check

Linked issues

Closes #979
Closes #980
Closes #981
Closes #982