docs(vibe): bootstrap vibe/ knowledge tree + ecosystem AGENTS.md

Add a root AGENTS.md (ecosystem map of factory/tools/cms + agent operating
rules + the persona cohort & workflow) and a new vibe/ knowledge base for LLM
agents, modeled on tree-docs conventions and the factory house style.

vibe/ folders (each with a README hub + contribution rules):
- ADR/      optimized MADR-lite; canonical home going forward (doc/adr stays historical)
- PRD/      one subfolder per PRD, mandatory STATUS.md, QA strategy for big ones
- investigations/  single INV-NNN-slug.md, or stub + folder w/ notebooks
- guidebooks/      tree-docs maps; lab-ecosystem guidebook of factory+tools+cms
- runbooks/        [AGENT]/[HUMAN] step procedures (EN; doc/runbooks stays FR)
- shareouts/       dated FR handouts (decks/mp4)

Seed content (first ADR + PRD): a safe, production-like environment to rehearse
risky changes and recovery without touching real prod — local-only sandbox
(k3d + arm64 VMs) with a hard prod/sandbox isolation boundary. Includes
INV-001 (prod blast-radius couplings), the ecosystem guidebook, and a FR shareout.

Conventions enforced: no-tombstone rule, breadcrumb spine, bidirectional
cross-links, theme:base mermaid (MCP-validated) + ordered-list-after-diagram.
Built with a Workflow + persona cohort; 24 files, zero dead links.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

vibe/runbooks/_template.md

@@ -0,0 +1,80 @@
+<!--
+COPY THIS FILE to start a new agent-oriented runbook.
+1. cp _template.md <kebab-case-name>.md
+2. Replace the breadcrumb's bold last item with the new page title.
+3. Fill every section below; delete this comment and all <…> placeholders.
+4. Tag EVERY procedure step [AGENT] (read-only/safe) or [HUMAN] (prod-mutating, needs explicit approval). When in doubt, use [HUMAN].
+5. Add a row for the new runbook to runbooks/README.md and wire any bidirectional links.
+-->
+
+[vibe](../README.md) > [Runbooks](README.md) > **_template**
+
+# <Runbook title — imperative, e.g. "Run the local sandbox game-day">
+
+> **Status:** ⬜ Not started
+> **Audience:** LLM agents (English). For the human-operator equivalent see the French [doc/runbooks](../../doc/runbooks/README.md).
+> **Last Updated:** 2026-06-23
+
+## TL;DR
+
+> [!TIP]
+> <One or two sentences: what this runbook accomplishes and the single most important thing to know before starting. State up front which steps an agent may run alone and where the human approval gate sits.>
+
+## Scope
+
+<What this runbook covers, and explicitly what it does NOT cover. Name the systems touched (Gitea, Postgres, Vault, k3s, ArgoCD, …) and the `<app>` or environment in play.>
+
+## Preconditions
+
+<Bulleted, verifiable preconditions that must hold before the procedure runs. Examples:>
+
+- [ ] Working in a worktree under `.claude/worktrees/<slug>/` (never the trunk).
+- [ ] Access to <Vault role / k3s context / Gitea repo> confirmed.
+- [ ] <Any backup taken / snapshot exists / CLUSTER_RECOVERY.md unseal key available>.
+
+## Procedure
+
+<Ordered steps. Each step is tagged [AGENT] (read-only/safe) or [HUMAN] (prod-mutating, requires explicit approval). Put copy-paste commands in fenced bash blocks owned by the step.>
+
+1. **[AGENT]** <Inspect current state / dry-run — safe, no mutation.>
+
+   ```bash
+   # read-only example
+   kubectl --context <ctx> get pods -n <app>
+   ```
+
+2. **[AGENT]** <Generate files, render manifests, run sandbox tests — safe.>
+
+   ```bash
+   # safe generation / sandbox example
+   tofu -chdir=<path> plan
+   ```
+
+3. **[HUMAN]** <Prod-mutating step. STOP here for explicit approval before running.>
+
+   ```bash
+   # prod-mutating example — only after approval
+   tofu -chdir=<path> apply
+   ```
+
+4. **[HUMAN]** <Any further live mutation, each individually gated.>
+
+## Verification
+
+<How to confirm the runbook succeeded. Prefer [AGENT]-runnable, read-only checks with expected output.>
+
+```bash
+# verification example
+kubectl --context <ctx> get application <app> -n argocd -o jsonpath='{.status.sync.status}'
+# expected: Synced
+```
+
+## Rollback
+
+<How to undo each prod-mutating step if verification fails. Tag each rollback action [AGENT] or [HUMAN] just like the procedure. Reference CLUSTER_RECOVERY.md by name for full power-cut/cluster recovery (it lives outside this repo — name only, no link).>
+
+## References
+
+- <Related guidebook page, e.g. [Lab ecosystem](../guidebooks/lab-ecosystem/README.md)>
+- <Related ADR under [doc/adr](../../doc/adr/README.md)>
+- <Human-operator equivalent under [doc/runbooks](../../doc/runbooks/README.md)>