feat: build system transition to release fork + archive hardening

Release fork infrastructure:
- REDBEAR_RELEASE=0.1.1 with offline enforcement (fetch/distclean/unfetch blocked)
- 195 BLAKE3-verified source archives in standard format
- Atomic provisioning via provision-release.sh (staging + .complete sentry)
- 5-phase improvement plan: restore format auto-detection, source tree
  validation (validate-source-trees.py), archive-map.json, REPO_BINARY fallback

Archive normalization:
- Removed 87 duplicate/unversioned archives from shared pool
- Regenerated all archives in consistent format with source/ + recipe.toml
- BLAKE3SUMS and manifest.json generated from stable tarball set

Patch management:
- verify-patches.sh: pre-sync dry-run report (OK/REVERSED/CONFLICT)
- 121 upstream-absorbed patches moved to absorbed/ directories
- 43 active patches verified clean against rebased sources
- Stress test: base updated to upstream HEAD, relibc reset and patched

Compilation fixes:
- relibc: Vec imports in redox-rt (proc.rs, lib.rs, sys.rs)
- relibc: unsafe from_raw_parts in mod.rs (2024 edition)
- fetch.rs: rev comparison handles short/full hash prefixes
- kibi recipe: corrected rev mismatch

New scripts: restore-sources.sh, provision-release.sh, verify-sources-archived.sh,
check-upstream-releases.sh, validate-source-trees.py, verify-patches.sh,
repair-archive-format.sh, generate-manifest.py

Documentation: AGENTS.md, README.md, local/AGENTS.md updated for release fork model

mk/config.mk

@@ -101,6 +101,11 @@ endif
 ifeq ($(REPO_OFFLINE),1)
 	export COOKBOOK_OFFLINE=true
 endif
+ifneq ($(REDBEAR_RELEASE),)
+	export REDBEAR_RELEASE
+	REPO_OFFLINE=1
+	export COOKBOOK_OFFLINE=true
+endif
 ifeq ($(REPO_DEBUG),1)
 	export COOKBOOK_NOSTRIP=true
 	export COOKBOOK_DEBUG=true

mk/repo.mk

@@ -39,6 +39,9 @@ endif
 
 # Fetch all recipes source or binary from filesystem config
 fetch: $(FSTOOLS_TAG) FORCE
+ifneq ($(REDBEAR_RELEASE),)
+	$(error fetch is disabled in release mode (REDBEAR_RELEASE=$(REDBEAR_RELEASE)). Sources are immutable.)
+endif
 ifeq ($(PODMAN_BUILD),1)
 	$(PODMAN_RUN) make $@
 else