docs: remap ASPF fingerprint design anchors to live code

[mikemol]

Motivation

• The fingerprint/identity design doc referenced abstract placeholders (e.g. identity_space.py / IdentityProjection) that are not part of the live codepath, which risks introducing orphan abstractions during implementation work.
• Anchor the design guidance to the concrete, authoritative implementation surfaces so future changes target the code that actually shapes canonical identity and evidence payloads.

Description

• Updated docs/aspf_fingerprint_contract.md and bumped doc_revision to 2 to remap identity guidance to existing code anchors.
• Added a Current-state map (live codepath anchors) section that lists the exact files and symbols to edit: src/gabion/analysis/aspf_core.py (AspfOneCell, AspfCanonicalIdentityContract), src/gabion/analysis/type_fingerprints.py (fingerprint_to_aspf_path, fingerprint_identity_payload), and src/gabion/analysis/evidence_keys.py (fingerprint_identity_layers).
• Added a Remapping gate section requiring proposals to explicitly map to those touchpoints and prohibiting new semantic-core wrappers (for example identity_space.py, IdentityProjection, or canonical_site_identity) unless a temporary adapter is justified with lifecycle metadata per policy.

Testing

• Attempted to run the ambiguity-contract policy check via mise exec -- python -m scripts.policy_check --ambiguity-contract, but the run failed due to local environment/tooling bootstrap issues (mise.toml trust / tool resolution and missing installed package in the resolved interpreter).
• Ran mise trust /workspace/gabion/mise.toml which completed, but mise exec still failed due to offline/toolchain resolution and a missing gabion module in the resolved Python; running .venv/bin/python -m scripts.policy_check also failed because no .venv exists in this environment.
• No unit tests or runtime code were modified; this is a documentation-only change and therefore did not alter test artifacts.

---

Codex Task