V48 (specification-implementation): Conform VCS providers to vcs-generics hierarchy

Enforce hierarchy for GitHub, GitLab, and Bitbucket: each provider extends
VCSProvider and implements AbstractVCSProvider under generic-vcs/*. Wire MCP
tools to hierarchy packages; flesh Bitbucket auth/connections via primitives;
update INTEGRATIONS and factory registration tests.

Author: geraldarthurdavis

BITCODE_SPEC_V48_NOTES.md

@@ -1658,6 +1658,20 @@ See “Artifact storage providers + remove @bitcode/aws” — providers split i
 `generic-artifacts/{aws,supabase,vercel}`; patch remains the type base;
 `@bitcode/artifacts` composes storage.
 
+## VCS provider conformity (Garrett, 2026-07-13)
+
+All VCS providers (GitHub, GitLab, **Bitbucket**) conform to:
+
+```
+@bitcode/vcs-generics
+  → @bitcode/generic-vcs-{github|gitlab|bitbucket|git}
+```
+
+Providers extend `VCSProvider` and implement `AbstractVCSProvider`. Factory
+registers lazy loaders into `generic-vcs/*`. MCP tools depend on hierarchy
+packages (not only shims). Shims `@bitcode/{github,gitlab,bitbucket,vcs,git}`
+remain BC re-exports.
+
 ## Artifact storage providers + remove @bitcode/aws (Garrett, 2026-07-13)
 
 ```

FAMILIARIZATION.md

@@ -272,14 +272,17 @@ Removed: `vcs`, `url`. VCS attaches as **external**.
 ```
 @bitcode/vcs-generics                      VCS primitives (AbstractVCSProvider, factory, service)
         ↑
-@bitcode/generic-vcs-{github|gitlab|bitbucket}   Provider implementations
+@bitcode/generic-vcs-{github|gitlab|bitbucket}   Provider bases (implements AbstractVCSProvider)
 @bitcode/generic-vcs-git                   Git-shaped bridge over providers
         ↑
-@bitcode/generic-tools-vcs / generic-agents-vcs   Tools + agent over VCS
+@bitcode/generic-tools-vcs / generic-agents-vcs / mcps-tools/{github,gitlab,bitbucket}
 ```
 
 Package paths: `packages/vcs-generics/`, `packages/generic-vcs/*`.
-Compatibility shims: `@bitcode/vcs`, `@bitcode/github`, …
+
+**Law:** every VCS provider lives under `generic-vcs/<provider>` and extends
+`VCSProvider` from `vcs-generics`. Shims `@bitcode/{vcs,github,gitlab,bitbucket,git}`
+are BC re-exports only.
 
 ### 3.2 Tools