feat: reorganize AHP around channels (RFC #117)

.github/instructions/general-instructions.instructions.md

@@ -35,7 +35,6 @@ applyTo: 'types/**/*.ts'
   ```
 
 - `number` types are assumed to be 64-bit integers. If a floating point values are reasonable for a field, you MUST annotate its jsdoc with `@format float`
-- After making a change, always add compatibility checks to the resulting file (current tip: `types/version/v2.ts`) so that any future incompatible changes will be caught by the compiler. See [Versioning](../../docs/specification/versioning.md) for details.
 - For actions or commands that could be implemented by returning an array `T[]` directly, still prefer to wrap it in `{ items: T[] }` for forward compatibility. This allows adding additional fields later without breaking the shape.
 - After making your changes, check to make sure the documentation in `docs` is up to date. For significant new flows or features, consider adding new documentation for it. Note that Mermaid diagrams are allowed.
 - Whenever you change or add an action, you must review the reducers in `types/reducers.ts` to see if that needs to be propagated into the state. If it does, add the appropriate logic and unit tests for it.

clients/rust/crates/ahp-types/README.md

@@ -31,7 +31,8 @@ serde_json = "1"
 use ahp_types::actions::{ActionEnvelope, StateAction};
 
 let json = r#"{
-  "action": { "type": "session/titleChanged", "session": "copilot:/s1", "title": "Hi" },
+  "channel": "ahp-session:/s1",
+  "action": { "type": "session/titleChanged", "title": "Hi" },
   "serverSeq": 7,
   "origin": null
 }"#;