docs(plugin): fix inaccuracies and flag real gaps found building a plugin

Found while building an out-of-tree scripting plugin from scratch against
this doc and the actual ocs_plugin_api/host source. Two categories:

Fixed outright (docs/examples didn't match the real code):
- The worked CadModule example returned Vec<RibbonGroup> from
  ribbon_groups(); the real trait requires &[RibbonGroup] - the example
  wouldn't compile. Fixed with the OnceLock pattern the host's own
  benchmark code already uses.
- Reconciled a contradiction between "process isolation removes the need
  for a shared Rust ABI" and the exact-rustc_version requirement described
  a few paragraphs earlier in the same doc.
- The roadmap's "Next" list still had external automation as unstarted;
  --mcp/--serve are real and operational (src/cli.rs, src/mcp.rs).
- Added the missing plugin.toml to docs/plugin-template-v2 (its own
  DESIGN.md already claimed one could be installed).
- Documented that plugin-template's CI floats rust-toolchain@stable, which
  doesn't guarantee matching the host's exact rustc - added acadrust_source
  to both templates' plugin.toml plus the release.yml step that fills it
  from Cargo.lock's resolved acadrust source, alongside the existing
  rustc_version fill.

Flagging for your call, not fixed here (found the behavior, not sure it's
the intended one, prefer to ask than guess at a fix):
- acadrust_compatible()'s ABI gate only runs at all if plugin.toml declares
  acadrust_source - an undeclared field is silently treated as compatible,
  unlike rustc_version (undeclared = incompatible). The same shortcut
  appears in two places: ExternalPlugin::acadrust_compatible
  (src/plugin/external.rs) and the inline check inside fetch_release_info
  (src/plugin/marketplace.rs). If this is deliberate (e.g. back-compat with
  manifests from before the field existed), no action needed beyond a
  comment; if not, both call sites need the same fix.
- The command line still uppercases typed/pasted input even with the `>`
  literal-spaces prefix (Message::CommandInput, src/app/update/mod.rs) -
  `>` only stops a space from auto-submitting the line, it doesn't skip
  `s.to_uppercase()`. A plugin command needing a case-sensitive typed
  argument has no escape today short of automation.
- fetch_release_info (src/plugin/marketplace.rs) returns every release
  under a linked repo with no filter on the manifest's own id field (which
  it already parses to build ReleaseInfo) - a repo hosting more than one
  plugin under tag-namespaced releases surfaces all of them mixed
  together in one plugin's version list.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/plugin-template/.github/workflows/release.yml

@@ -29,6 +29,14 @@ jobs:
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v4
+      # NOTE: @stable floats to whatever's current when this job runs, which
+      # is NOT the same thing as "matches the host's rustc exactly" — the API
+      # v4+ load check compares plugin.toml's rustc_version to the host's
+      # build-time compiler byte-for-byte (see plugin-architecture.md's
+      # "Build-time ABI metadata"). Pin this to the host's actual toolchain
+      # version (check crates/ocs_plugin_api/src/version_info.rs's embedded
+      # value, or the host's own CI config) before a real release, or your
+      # binary may be refused at load with a version-mismatch error.
       - uses: dtolnay/rust-toolchain@stable
       - run: cargo build --release
       - name: Stage release asset
@@ -36,7 +44,11 @@ jobs:
         run: |
           mkdir -p dist
           cp target/release/*.${{ matrix.ext }} "dist/${{ matrix.asset }}"
-          sed "s|__RUSTC_VERSION__|$(rustc --version)|" plugin.toml > dist/plugin.toml
+          acadrust_source=$(grep -A3 '^name = "acadrust"' Cargo.lock | grep '^source' | head -1 | sed 's/^source = "//;s/"$//')
+          sed \
+            -e "s|__RUSTC_VERSION__|$(rustc --version)|" \
+            -e "s|__ACADRUST_SOURCE__|$acadrust_source|" \
+            plugin.toml > dist/plugin.toml
       - uses: softprops/action-gh-release@v2
         with:
           files: |