Expand azure-search-documents skill with full release workflow

The existing skill on main covered only the post-regeneration _patch.py audit (SKILL.md + customizations.md). This commit expands it into the full release workflow (Phase 0-7: scope, generate, sync, test, lint, changelog, samples, version) and reorganizes the customization material so each file has a single concern.

- SKILL.md: rewritten as the workflow backbone; _patch.py reconciliation is now Phase 2 of a larger pipeline.

- references/architecture.md (new): source layout, branching strategy, CHANGELOG conventions.

- references/testing.md (new): unit and live test workflow.

- references/customizations.md: Generated-vs-Handwritten rules, _patch.py map, Patterns Reference, per-file inventory (lifted out of SKILL.md tail and architecture material).

- scripts/run-in-venv.ps1 (new): portable per-call wrapper that resolves the package .venv from any CWD.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: hizixin