refactor(identity): consume canonical implementation immutably

[szmyty]

Summary

• replace Empathy's duplicated identity/ implementation tree with a Git submodule pinned to exact canonical Identity commit 73e7add02dbd11c38cf8a76d03d7ef2219e252ac
• add .config/identity/consumer-lock.json so the reviewed repository, revision, extraction lineage, consumer, and governing issue are explicit
• preserve all existing local command paths through identity/Cargo.toml
• verify the gitlink, lock, and initialized worktree all resolve to the same immutable commit before any Identity task runs
• update Identity CI to initialize the pinned source and rerun locked dependency resolution, formatting, strict Clippy, Rust tests, Empathy integration checks, validation, and deterministic handoff
• document review, update, authority, and rollback procedures
• keep Empathy's .identity/ intent and assets/identity/ consumer outputs repository-owned

Architecture transition

before
Empathy
  ├── .identity/                 consumer intent
  └── identity/                  duplicated canonical implementation

                  ↓

after
Empathy
  ├── .identity/                 consumer-owned intent
  ├── assets/identity/           generated consumer projections
  ├── identity                   gitlink to exact canonical commit
  └── consumer-lock.json         duplicate-aware reviewed pin

Canonical implementation owner: egohygiene/identity

The consumer does not follow main, a release tag, or git submodule update --remote. A reviewed update changes the gitlink and lock together.

Consumer validation

The revised integration tests verify:

• identity is mode 160000 in Empathy's Git tree
• the gitlink revision equals the consumer lock
• the initialized submodule worktree equals the same revision
• the canonical v0 contracts and eight preserved profiles remain available
• all 45 target/profile assumptions remain checked through the existing consumer tests
• task and workflow adapters invoke the pinned CLI
• consumer intent continues to require human approval

Rollback

Revert this transition commit to restore the prior incubated source tree. Pin-only updates restore the previous gitlink and lock together. Neither path rewrites or deletes .identity/.

Contributes to egohygiene/identity#8.