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/index.md

@@ -78,10 +78,3 @@ Planned future features (no dates; tracked in the internal roadmap):
 - [Consumer Guide](consumer-guide) — start here if you are a consumer.
 - [Architecture](architecture) — start here if you are a platform engineer.
 - The [README](https://github.com/nova/nova) describes the platform repo.
-
-> **Note:** The product brand is **Nova** (formerly ACDL — Agentic Cloud
-> Delivery Platform). The Gitea repository name (`continuous-intelligence/acdl`)
-> and the GitHub `uses:` reference (`acdl/.github/workflows/deploy.yml@…`)
-> are unchanged during the rebrand transition; only the product name is
-> changing. See the [Nova migration guide](NOVA_MIGRATION) for the
-> scheduled breaking changes.