feat(P1): remove gitea/gitlab from synced files + simplify docs (REQ-230,231,232)

Genericize forge-detection code: gitea→forge/generic_forge, GITEA_ACTOR→FORGE_ACTOR.
Drop .gitea byte-identity test assertions (keep GitHub-side + contract conformance).
Add test_no_forge_mentions.py guard test (REQ-230).
Delete completed migration docs (NOVA_MIGRATION.md, NOVA_AWS_MIGRATION.md).
Move NO_HUMANS_THESIS.md to .ciagent/ (internal artifact).
Strip ciagent-internal provenance from synced docs (REQ-/D-/P-/CAP- IDs,
milestone headers, .ciagent/PROJECT.md citations).
Trim README.md (reusable deploy section, local key rotation paragraph).
Fix version-tag drift (@v1.13→@v1.19, acdl/→nova/).

---ci---
project: acdl
phase: 1
milestone: v1.20
status: execute
requirements: [REQ-230, REQ-231, REQ-232]
---/ci---

docs/skills.md

@@ -34,14 +34,14 @@
 
 ## Atelier Provenance
 
-The skills are derived from [Atelier](https://git.cloudinit.dev/coreci/atelier)
+The skills are derived from [Atelier](https://example.com/atelier)
 — a first-principles docs-as-code engineering framework with 8 core
 principles (C1–C8) and 19 domains, each with 10 derived P-rules. The
 skills distill the citizen-developer-relevant subset of each domain's
 first-principles, link to the agent-checklist triggers, and map to the
 existing BA.A catalog.
 
-Atelier is vendored under `mcp/atelier/vendor/` (pinned tag, D-136) for
+Atelier is vendored under `mcp/atelier/vendor/` (pinned tag) for
 audit reproducibility — an agentic validation result is replayable
 against the exact principles that produced it.