ci: standardize workflows and chart patterns to match org playbook

[devin-ai-integration]

Summary

Aligns qcon-guide's workflows and docs with the qcon-api reference implementation. Most patterns were already standardized from a prior pass — this PR addresses the remaining gaps:

• pr-title-lint.yaml: Replaced verbose sticky-comment failure message with qcon-api's concise version (shorter heading, bullet-style examples, one-liner edit hint).
• release-please.yaml: Added the 2-line comment above dispatch-publish explaining why explicit dispatch is needed (GITHUB_TOKEN releases don't trigger downstream workflows).
• AGENTS.md: Removed duplicate CI/publish bullets from Deployment section (already covered in CI/CD section).

All other playbook patterns (FORCE_JAVASCRIPT_ACTIONS_TO_NODE24, checkout@v6, helm push error guard, tolerant digest parse, yq chart name extraction, shell-safe GHA expressions, digest guard on sign steps, Chart.yaml annotations, release-please-config.json, affinity conditional) were already matching the reference.

Review & Testing Checklist for Human

• Verify the pr-title-lint sticky comment renders correctly on a failing PR (formatting, emoji, code blocks)
• Confirm release-please dispatch still triggers helm-publish and release-retag on next release

Notes

• Helm lint passes: 1 chart linted, 0 failed
• Kubeconform passes: 3 resources valid, 0 invalid
• No functional workflow changes — only comments and documentation

Link to Devin session: https://app.devin.ai/sessions/ee3ef5b17ac74a99be13392c18df2f5c
Requested by: @kphunter

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.