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---

pipelines/ci.yml

@@ -1,7 +1,7 @@
 # Nova Central CI Pipeline Contract (v1.5)
 #
 # This is the single source of truth for the CI/CD pipeline. Both
-# .gitea/workflows/ci.yml (Gitea Actions, dev) and
+# .github/workflows/ci.yml (dev) and
 # .github/workflows/ci.yml (GitHub Actions, production) implement the
 # stages, commands, triggers, and runner declared here.
 # scripts/run_ci.sh mirrors the same stages for shell reproducibility.
@@ -11,7 +11,7 @@
 #
 # The contract does NOT replace workflow YAML syntax — it declares the
 # *intent* that the forge-specific workflows implement. The workflow files
-# use Gitea/GitHub Actions syntax (checkout, setup-python, run blocks);
+# use GitHub Actions syntax (checkout, setup-python, run blocks);
 # this contract declares what those blocks must contain.
 #
 # Validated against schemas/pipeline.schema.json.