README as landing page, practitioner docs, changelog, and repo health signals

[stempeck]

Executes the Tier A repo-content phases of the visibility plan.

What changed

• README.md — restructured as an indexable landing page: prose "Why agentfactory" opening, CI/Go/license/release badges, native Mermaid architecture diagram (skills → formulas → agents → sessions), an honest comparison table vs LangGraph/CrewAI/raw subagents, roadmap section linking real issues, author line. Formula table now reflects the 19 shipped formulas (was 5). Removed the manual .gitignore instruction — af install --init already writes .git/info/exclude.
• docs/formulas.md, docs/agent-lifecycle.md, docs/recovery-model.md — short practitioner pages, every command verified against internal/cmd/; cross-linked with each other and docs/architecture/.
• CHANGELOG.md — seeded from the full PR history, grouped by theme, for the upcoming v0.1.0 release.
• Issue templates — standard bug/feature templates alongside the existing agent-dispatch default.
• .github/workflows/visibility-health.yml — monthly watchdog: verifies topics, description, release presence, and README badges; opens one issue on regression, never commits.

Verification

• Docs commands cross-checked against CLI source by a dedicated verification pass (one invented gate type caught and removed before commit).
• Markdown/workflow changes only — no Go code touched; make test not applicable.

🤖 Generated with Claude Code