Migrate package guides to the canonical PHP documentation flow #31

Current contract

The user clarified that the existing Fast Forward PHP documentation flow is required. The DevTools sphinx-docs skill describes reStructuredText content/navigation; it does not require a Python renderer. Do not introduce conf.py, sphinx-build, a new documentation engine/template repository, or a runtime dependency on DevTools.

• Preserve all unique architecture, policy, provenance, legacy comparison and bootstrap content while migrating the eight superseded Markdown documents to one navigable RST tree.
• Remove the replaced files and update README, instructions, toctrees and references; no orphaned or duplicate authoritative pages.
• Use the existing PHP DevTools reports:docs command, phpDocumentor and Fast Forward template from an isolated documentation-tool installation. No new deployment workflow or authoring-skill import.
• Build the actual HTML, inspect navigation/assets/inventory references and generated API links, and record precise unresolved targets rather than claiming the whole output is clean.
• Independent review and current-HEAD CI/bot gates remain required before integration.

PR #29 implements the migration. Current qualification found two generated API/template targets needing resolution or a documented domain decision: Interop-Container-ServiceProviderInterface.html and graphs/classes.svg. All 21 RST guide pages are reachable and their navigation targets exist; that does not make the complete rendered API link check pass. Keep this issue open while this acceptance item remains unresolved.