docs(refactor): align plugin SDK plan with public capability model

Add capability plan alignment section with key decisions and required test
matrix. Rename seams to capabilities for consistency.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/refactor/plugin-sdk.md

@@ -213,7 +213,33 @@ Notes:
 
 Related docs: [Plugins](/tools/plugin), [Channels](/channels/index), [Configuration](/gateway/configuration).
 
-## Implemented channel-owned seams
+## Capability plan alignment
+
+The plugin SDK refactor now aligns with the public capability model documented
+in [Plugins](/tools/plugin#public-capability-model).
+
+Key decisions:
+
+- Capabilities are the public plugin model. Registration is explicit and typed.
+- Legacy hook-only plugins remain supported without migration.
+- Plugin shapes (plain-capability, hybrid-capability, hook-only, non-capability)
+  are classified from actual registration behavior.
+- `openclaw plugins inspect` provides canonical deep introspection for any
+  loaded plugin, showing shape, capabilities, hooks, tools, and diagnostics.
+- Export boundary: export capabilities, not implementation convenience. Trim
+  non-contract helper exports.
+
+Required test matrix for the capability model:
+
+- hook-only legacy plugin fixture
+- plain capability plugin fixture
+- hybrid capability plugin fixture
+- real-world legacy hook-style plugin fixture
+- `before_agent_start` still works
+- typed hooks remain additive
+- capability usage and plugin shape are inspectable
+
+## Implemented channel-owned capabilities
 
 Recent refactor work widened the channel plugin contract so core can stop owning
 channel-specific UX and routing behavior:
@@ -234,5 +260,5 @@ channel-specific UX and routing behavior:
   config mutation/removal
 - `allowlist.supportsScope`: channel-owned allowlist scope advertisement
 
-These hooks should be preferred over new `channel === "discord"` / `telegram`
-branches in shared core flows.
+These capabilities should be preferred over new `channel === "discord"` /
+`telegram` branches in shared core flows.