add bin/arcodange CLI and dolibarr-tva-summary skill

Two changes that go together: now operators can run every read-only
workflow without going through Claude. The skills (SKILL.md files)
remain the source of behaviour documentation and Claude triggers;
bin/arcodange is the human-facing entry point.

bin/arcodange:
- Bash dispatcher at the project root. Subcommands per domain:
  tva {collect, collect-detail, deductible, deductible-detail, summary},
  invoice {list, audit}, thirdparty {audit, audit-all},
  payments {state, timeline, by-month},
  templates {list, inspect},
  snapshot, whoami, ping, curl, help.
- Locates the project root via `git rev-parse` so it works from any
  CWD (including from a worktree).
- Per-subcommand `help` text. Unknown commands exit 2 with a hint.
- Reuses the existing per-skill scripts under .claude/skills/<name>/
  scripts/ via `exec` (zero behaviour drift, full credit to the
  existing tested code).

dolibarr-tva-summary:
- Composes dolibarr-tva-reconciliation (TVA collectée customer-side)
  and dolibarr-tva-deductible (TVA déductible supplier-side) into a
  single CA3-ready monthly summary with per-month net verdict
  (TVA à reverser / crédit de TVA / équilibre) and a cumulative line.
- Live baseline: Arcodange en crédit de TVA de 223.22 € cumulé
  (0 € collectée 259-1° CGI vs 223.22 € déductible).
- Exposed as `arcodange tva summary [--year|--since|--until]`.

Each existing skill's SKILL.md gets a one-line "CLI shortcut" near
the top so the human path is discoverable from any skill page.
The project root README.md gets a CLI section as the primary
operator entry point.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.claude/skills/dolibarr-payments-state/SKILL.md

@@ -8,6 +8,8 @@ requires:
 
 # dolibarr-payments-state — KissMetrics cash-receipt tracking
 
+**CLI shortcuts:** `bin/arcodange payments state` · `bin/arcodange payments timeline` · `bin/arcodange payments by-month`
+
 This skill answers "**who owes Arcodange what, and when did they pay?**" against the live Dolibarr. It's the natural follow-up to [dolibarr-invoice-audit](../dolibarr-invoice-audit/SKILL.md): that one validates that a given invoice was emitted correctly; this one validates the money landed.
 
 Depends on the [dolibarr](../dolibarr/SKILL.md) base skill for the connection, the `.env`, and the `voir_tous` permission flags. The existing **Factures → Voir toutes** flag from V1 is sufficient — payments are nested under invoices (`/invoices/{id}/payments`), and there's no `/payments` list-all endpoint (501 Not Implemented).