Align edit-base documentation with current runtime and packaging contracts

[OliverZhaohaibin]

Summary

Synchronizes the edit-base documentation with the current runtime, recognition, packaging, and release contracts in one pass.

P0 completed

• docs/architecture.md: DesktopCoordinatorRuntime, lightweight entrypoint, feature-driven recognition activation, Pets persistence/model/runtime contracts.
• AGENT.md: adds Pets as a first-class bounded context and documents current startup/coordinator/model rules.
• docs/misc/PETS_RECOGNITION_RUNTIME.md: species-bounded-single-link-v3, anti-chaining/diameter constraints, current People/Pets overlap arbitration, feature-driven scan activation.
• docs/development.md: fixes iPhoto.entrypoint:main, coordinator/startup semantics, i18n canonical path, model staging and DINO provisioning.
• docs/CHANGELOG.md: replaces stale Unreleased startup semantics with the final implementation and clearly separates Unreleased work from v6.6.8.
• README.md, docs/readme/README_zh-CN.md, docs/readme/README_de.md: aligned release-vs-development semantics and verified v6.6.8 artifact names across all maintained languages.
• docs/security.md: separates Torch Hub/source provenance from production TorchScript artifact trust; documents torchscript_url: null and staging behavior.
• docs/misc/BUILD_DEB.md: removes 5.00-era instructions and aligns with dist/entrypoint.dist and pyproject.toml versioning.

P1 completed

• Added docs/misc/BUILD_APPIMAGE.md matching scripts/build_appimage.sh.
• Added docs/misc/BUILD_FLATPAK.md: published v6.6.8 artifact is explicitly distinct from current reproducible source-build support.
• Rebuilt docs/requirements/scan_c_hotspot_optimization.md as a current profiling/rebaseline requirement; removed obsolete scanner call graphs/timings.
• Added docs/requirements/pets-cluster/README.md marking old clustering documents historical/superseded and pointing to the canonical runtime contract.
• Added docs/requirements/README.md defining Active, residual-debt, Historical/Superseded, and Finished lifecycle states. Startup optimization remains in requirements because residual debt is still documented.

P2 completed

• Added tools/check_readme_parity.py to enforce EN/ZH/DE release artifact and core runtime-contract parity.
• Added tools/check_docs_links.py to detect broken repository-local Markdown links.
• Added tests/architecture/test_docs_contracts.py; the existing Tests workflow already runs the full tests/ tree on PRs to edit-base, so these checks execute in CI without adding a new workflow permission surface.

Source-of-truth contracts

• GUI console script: iPhoto.entrypoint:main.
• Desktop composition root: DesktopCoordinatorRuntime; main_coordinator.py is compatibility-only.
• Recognition inference activates after People is shown and its first viewport is ready, not at application startup.
• Pets clustering: species-bounded-single-link-v3.
• Strong face overlap normally suppresses a pet candidate, with the current larger plausible pet-body preservation exception.
• Production DINOv2 loads a prebuilt hash/size-verified TorchScript artifact. The current manifest has torchscript_url: null; package/staging is required for DINOv2.
• src/extension/models/... is a packaging/staging convention, not guaranteed fresh-clone content.

Validation

• v6.6.8 Release assets were checked against GitHub before aligning all three README files. The Windows artifact is actually named v6.68-x86-setup.exe.
• Documentation contract tests are included in the existing pytest CI path.
• PR remains Draft until the current CI run is checked.