fix(harness): migrate legacy cursor install-state into profile sync

[solomonneas]

Summary

Closes #468.

brigade harness install cursor --scope user (legacy, cursor_user_cmd.py, schema v1) and brigade harness sync --target cursor --scope user (profile layer, harness_profile_cmd.py, schema v2) share ~/.cursor/brigade/install-state.json with incompatible schemas. Each refused the other's state as a conflict with no recovery path — a deadlock whose only manual escape (rm the state file) also destroys the ownership attestations uninstall needs.

Root-cause fix (option 1 from the issue): the legacy installer is already documented as superseded by sync, so the profile layer now detects a legacy version-1 state and deliberately migrates it:

• harness_profile_cmd.load_profile_state detects {"version": 1, ...} on the cursor harness and adopts every legacy attestation into the v2 ownership model — instruction digest, generated plugin/hook artifacts, the hooks.json#sessionStart entry fingerprint, skill files, and MCP projections (the legacy digest prefix is stable_hash-compatible, so unedited live entries still attest). Adoption is in-memory and read-only until a sync --write persists the migrated state; the result payload reports "migration": {"from": "legacy-install-v1", ...}.
• The sync then proceeds normally: legacy-owned artifacts reconcile as current, the superseded brigade/mcp.json catalog and legacy-only skill files are removed through the standard removed-profile/removed-registry paths, and nothing user-owned is clobbered.
• Reverse direction: legacy harness install cursor after a profile sync now fails closed with a conflict that names the recovery step — run brigade harness uninstall --target cursor --scope user from the owning surface first — instead of a bare unsupported ownership state version: 2.

No other harnesses' behavior changes (migration is gated on harness == "cursor" and the legacy v1 shape; non-cursor and malformed states keep the existing fail-closed error).

Tests

• test_cursor_legacy_install_migrates_into_profile_sync: legacy install → profile sync migrates cleanly (rule survives byte-for-byte, attestations carried), a second sync is a no-op, and harness uninstall --scope user removes exactly the artifacts — originally-legacy and newly-synced alike.
• test_cursor_profile_sync_then_legacy_install_names_recovery: profile sync → legacy install gives the recovery-named conflict, writes nothing, and leaves the v2 state untouched.
• test_load_state_migrates_legacy_cursor_install_state_read_only / test_load_state_rejects_non_dict_legacy_cursor_sections: unit coverage for the adoption mapping, read-only guarantee, and fail-closed edges.

All tests drive a temp HOME/tmp_path; the real ~/.cursor is never touched.

Verification (brigade-wired)

brigade work verify run --target . --command "pytest -q tests/test_harness_user_scope_slice2.py tests/test_harness_profile_cmd.py" --capture brigade-work
# status: completed — exit=0 (55 passed)

brigade work verify run --target . --command "./scripts/verify" --capture brigade-work
# status: completed — exit=0 (ruff, ruff format, mypy, version sync; 4186 passed, 3 skipped)

Receipts: .brigade/work/verify-runs/20260724-002316-work-verify-322e6a/ and .brigade/work/verify-runs/20260724-002456-work-verify-019210/.

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[solomonneas]

Superseded by #510, which is the later green fix for the same #468 Cursor install-state migration. Closing this duplicate without merging.