Return compact activation summaries instead of discovery schemas

Card: SAU-158

PROTOCOL.md

@@ -334,7 +334,7 @@ At start, the core starts each service in `/config/boot.yaml`, in order:
 | `core.kill` | `pid` | `{}` |
 | `core.lock` | `path`, `wait`? | `{"held": bool}` |
 | `core.unlock` | `path` | none (a notification) |
-| `core.activate` | `plugin` and `wasm`, or `plugins: [{plugin, wasm}]`. `force`? | the new `rpc.discover` documents |
+| `core.activate` | `plugin` and `wasm`, or `plugins: [{plugin, wasm}]`. `force`? | short activation summaries, keyed by plugin |
 | `core.revert` | `plugin`, `force`? | like `core.activate` |
 | `core.log` | filters (section 7) | journal entries |
 | `core.restart` | none | `{}`. With `SAUSAGE_LOOP=1`, schedule clean shutdown and exit code 75. |
@@ -434,6 +434,26 @@ imported method:
 If a check fails, nothing changes, and the error -32003 lists each problem,
 with a counterexample where possible.
 
+The result is an object keyed by plugin name. Each value contains:
+
+- `plugin`: the plugin name.
+- `wasm`: the installed world path (`/plugins/<name>/plugin.wasm`).
+- `hash`: the SHA-256 of the installed copy.
+- `previous`: the replaced version's SHA-256, or `null` on first installation.
+  For an identical-hash no-op, this is the current hash.
+- `method_count`: the number of methods in the new main interface.
+- `added`, `removed`, `changed`: sorted method-name arrays compared with the
+  previous discovery document. A change to a method description or any
+  transitively referenced local schema counts as changed. Unrelated schemas
+  and endpoint interfaces do not affect these arrays. With no previous
+  document, all methods are added.
+- `interface_check`: `"passed"` after successful checks, or `"skipped"` with
+  `force: true` (not a claim of compatibility).
+
+The result does not include schemas. The full document remains available
+through `<plugin>.rpc.discover` and `/proc/core/plugins/<name>/discover.json`.
+An identical-hash no-op and `core.revert` return the same summary shape.
+
 - The core runs one activation at a time.
 - `plugins: [...]` activates several plugins together. The checks then use
   the new set.