docs: onboarding guide for the autonomous loop and new-project setup (closes #19)

[robercano-ghbot]

What & why

Distills issue #19 into a single onboarding reference so a new adopter has one explicit path to configure the orchestrator — and understands the convention that trips people up: the autonomous loop only builds issues you have explicitly queued with a module:* label.

Changes

• docs/USAGE.md — new ## Autonomous loop & the issue queue section (placed with the existing loop mechanics): the per-tick order poll → merge → address-feedback → advance, the module:* label as an explicit opt-in work queue (lowest-numbered first, one at a time, only when zero open PRs; unlabelled issues never touched; label maps issue → module → the worker's path boundary), the owner-approval merge gate (bot authors PRs; the loop only merges owner-APPROVED, CI-green, mergeable PRs and never self-approves), and the corollary that non-module work isn't loop-eligible until its area is a module in gates.json.modules[] and the issue carries the matching label. Adds a one-line note that /pr-loop is the canonical definition of the tick order so the two loop descriptions can't drift.
• docs/GETTING_STARTED.md — new ## New-project configuration checklist: a copy-pasteable numbered list (gates.json fields, CLAUDE.md, bot machine account + GH_BOT_TOKEN in gitignored .env, module:* label creation, server-side gates workflow, /pr-loop arming + session-scoped re-arm caveat, optional /harden).
• README.md — links the checklist from the "Use it" onboarding section.
• docs/PROMPTS.md — "Brand-new project?" pointer near the top so a new project lands on the checklist + loop section first.
• .claude/scripts/seed-issues.sh — header NOTE (no logic change) documenting that this script is the module→label anti-drift mechanism, plus a bot-gh.sh label create "module:$m" --force one-liner to bootstrap labels-only through the bot.

Gates

Docs-only. gate.sh lint and gate.sh test_affected both report "not configured — skipping" (empty adapter, as expected for the template repo itself).

Review (consensus: all four lenses APPROVED)

• Correctness ✅ — tick order, queue rules, and merge gate verified against .claude/commands/pr-loop.md, merge-ready.sh, notify-poll.sh, pr-feedback.sh; all cross-links/anchors resolve.
• Tests/verifiability ✅ — bot-gh.sh confirmed a pass-through wrapper so the documented label create one-liner works; bash -n seed-issues.sh passes; gate claims match gate.sh output.
• Security ✅ — no secrets committed; .env correctly described as gitignored; least-privilege bot; owner-approval gate faithful; snippet has no injection/eval.
• Performance/conciseness ✅ — distillation not duplication; new module:* queue rationale is genuinely new; overlapping merge-gate content defers via cross-link.

Note for the owner

The single commit is unsigned: the owner's global git config enforces SSH commit signing, and this sandboxed run cannot read the signing key under ~/.ssh. Amend/re-sign locally if a verified commit is required (git commit --amend -S --no-edit); content is unchanged.

Closes #19