docs: AGENTS.md — orientation + backlog discovery for agents

Agents landing in this repo had no entry point: no AGENTS.md, and the
backlog (erp#38-57 on 6 dated milestones, gateway#1-2, factory#22)
was only discoverable from the PRD STATUS in the factory repo. This
seeds the repo-root orientation map: where the work comes from (resume
protocol: top unblocked issue of the earliest open milestone, gitea
MCP pointers, owner gotcha for telegram-gateway), the repo map, the
operating rules (trunk/worktrees, read-only prod, sandbox+promote
gate, append-only ledger, anti-hallucination contract pointers).

Advances erp#38 (AGENTS.md seed; the fleet/ scaffold and the full
fleet section remain in #38's scope).

Co-Authored-By: Claude Fable 5 <[email protected]>

AGENTS.md

@@ -0,0 +1,35 @@
+# erp — Dolibarr ERP & the AI back-office fleet
+
+This repo runs Arcodange's **Dolibarr 22.0.4 ERP** (the company's book of record) and hosts the tooling + AI-agent skills that operate its daily admin & accounting. Deployed by the factory ArgoCD app-of-apps: **prod** at `erp.arcodange.lab`, **iso-prod sandbox** at `erp-sandbox.arcodange.lab`. Ecosystem front door: [factory AGENTS.md](https://gitea.arcodange.lab/arcodange-org/factory/src/branch/main/AGENTS.md).
+
+## Where the work comes from — the backlog
+
+The [AI back-office PRD](https://gitea.arcodange.lab/arcodange-org/factory/src/branch/main/vibe/PRD/ai-back-office/README.md) is decomposed into **self-contained issues** on dated milestones. Each issue body carries its context, deliverables, acceptance criteria, dependencies and PRD links — no conversation history needed.
+
+- **Resume protocol: pick the top unblocked issue of the earliest open [milestone](https://gitea.arcodange.lab/arcodange-org/erp/milestones)** (P1 flagship → P2 e-invoicing *hard 2026-09-01* → P3 standing fleet → ledger compliance → P4 money loops → P5 fiscal).
+- From a session: `ToolSearch select:mcp__gitea__list_issues,mcp__gitea__issue_read`, then owner `arcodange-org`, repo `erp`. Related backlogs: [telegram-gateway issues](https://gitea.arcodange.lab/arcodange/telegram-gateway/issues) (owner `arcodange`, **not** arcodange-org) and [factory#22](https://gitea.arcodange.lab/arcodange-org/factory/issues/22) (ADR tracking).
+- Full phase tracker + backlog map: the PRD [STATUS.md](https://gitea.arcodange.lab/arcodange-org/factory/src/branch/main/vibe/PRD/ai-back-office/STATUS.md).
+
+## Map
+
+| Path | What |
+| --- | --- |
+| `chart/` | Helm chart (prod + sandbox overlay), backup CronJob, before-start SQL |
+| `ops/` | `sandbox/sandbox-lifecycle.sh` (iso-prod refresh), `backup/` (offsite db+docs, restore) |
+| `bin/arcodange` | operational CLI — read prod (invoices, payments, TVA, bank, templates, snapshot), sandbox writes, gated promote |
+| `.claude/skills/` | the skill catalog; each `SKILL.md` frontmatter carries its **Use when… / SKIP for…** triggers — read them before reinventing |
+| `test/` | Playwright provisioning POCs (sandbox write agent `ai_agent_sandbox`, rights in `provisionSandbox.ts` WRITE_IDS) |
+| `fleet/` | atom registry, class skeletons, golden sets — **not yet landed**, tracked by [erp#38](https://gitea.arcodange.lab/arcodange-org/erp/issues/38) |
+
+## Operating rules for agents
+
+- **Trunk is reserved for the user.** Work in a worktree under `.claude/worktrees/<slug>/` on an `arcodange/<slug>` branch. This forge is **Gitea** — use the `mcp__gitea__*` tools for PRs/issues; `gh` fails silently.
+- **Prod is read-only for agents** (`ai_agent` key from `.claude/skills/dolibarr/.env`, mode 600). Beware the `voir_tous` ACL trap: a missing permission returns empty lists, not errors.
+- **Writes rehearse on the sandbox first** (`ai_agent_sandbox`, host-guarded — structurally cannot reach prod), then reach prod only through the human-gated promote flow (`arcodange promote plan|apply`, prod key ENV-only + explicit confirm) — [ADR-0003](https://gitea.arcodange.lab/arcodange-org/factory/src/branch/main/vibe/ADR/0003-sandbox-state-lifecycle.md).
+- **Production is an append-only ledger**: create → validate → pay → avoir; never mutate or delete a validated document, never fabricate a ref Dolibarr owns. Full grammar + anti-hallucination write contract (provenance anchors, fresh-feed corroboration, refuse-never-repair): PRD [compliance](https://gitea.arcodange.lab/arcodange-org/factory/src/branch/main/vibe/PRD/ai-back-office/compliance.md) + [agent-architecture](https://gitea.arcodange.lab/arcodange-org/factory/src/branch/main/vibe/PRD/ai-back-office/agent-architecture.md).
+- Sandbox state is disposable: `bin/arcodange sandbox checkpoint {status|refresh|provision|relink-env}` (refresh re-seeds iso-prod and wipes the write agent → re-provision, human login). Anything irreversible-by-design is trialed on a checkpoint first.
+- Bank feeds (Qonto/Wise) and the Zoho mailbox are **read-only by construction**; no agent ever moves money.
+
+## Before building anything
+
+Read the PRD hub (5 min) — problem, autonomy ladder A0–A3, architecture, agent catalog. Then your issue. Then the SKILL.md of anything you touch. A change that leaves its `SKILL.md` stale is an incomplete change.