Update documentation to reflect recent features and simplify README

[sebastientaggart]

Problem to Fix

The project documentation has not kept pace with recent feature additions. Several skill reference pages are missing coverage of new capabilities like structured issue bodies, complexity indicators, post-review approval gates, and resolution comments. The README also reads more like technical documentation than a landing page for new visitors evaluating the project.

Why it Matters

First-time visitors rely on the README to decide whether Code Cannon fits their needs — a dense, documentation-heavy README can lose them before they reach the good parts. Meanwhile, existing users consulting the skill reference pages are not seeing the full picture of what the workflow now offers, which means they may not take advantage of recent improvements.

General Approach

Update the skill reference docs for /start and /submit-for-review to cover features added in recent PRs. Simplify the README into a focused marketing document that sells the value proposition quickly and links to docs for details. Light polish on general docs where needed.

Complexity

Verification / QA effort: moderate
All changes are documentation-only — verification involves reading the updated pages for accuracy, completeness, and tone consistency.

Acceptance Criteria

• docs/skills/start.md covers structured issue body sections, complexity indicator, and intent classification for human gates
• docs/skills/submit-for-review.md covers the post-review human gate for non-blocking findings and the resolution comment step
• README.md is shorter, scannable, and focused on selling the project to new visitors
• No broken internal links across docs
• General docs refreshed where needed to reflect current state

[sebastientaggart]

Agent Implementation Notes

Skill docs updates

docs/skills/start.md — three additions:

1. Add the five-section structured issue body format (Problem to Fix, Why it Matters, General Approach, Complexity, Acceptance Criteria) with explanation of each section's purpose
2. Document intent classification for human gates — how affirmative, conditional, question, and abandonment responses are handled
3. Add complexity scale guidance (trivial/moderate/significant/extensive) with brief descriptions

docs/skills/submit-for-review.md — two additions:

1. Add post-review human gate: when review finds non-blocking findings (warnings/notes), the agent asks whether to address them or merge now
2. Add resolution comment step: after merge, a plain-language summary comment is posted to the linked issue

README simplification

Target: ~70-80 lines (down from 126). Changes:

• Tighten problem/solution pitch
• Remove "GitHub baseline for PM/BA setup" section (move detail awareness to docs)
• Remove "Reviewer selection" implementation detail
• Trim philosophy to essentials
• Simplify quick start (just the 3 commands + link to docs)
• Remove detailed submodule update instructions (already in docs)
• Keep skill table but make it leaner

General docs

• Light refresh of docs/index.md if needed
• No changes expected for branching.md, customization.md, config-reference.md, adapters.md

[sebastientaggart]

Resolution

Updated the skill reference docs for /start and /submit-for-review to cover recent features like structured issue bodies, complexity indicators, intent classification for human gates, post-review approval gates, and resolution comments. Simplified the README from 126 to 77 lines, focusing it as a marketing page for first-time visitors while moving detailed setup instructions to the docs.

See #103 for full technical details.