refactor: unify peer kind to ChatType, rename dm to direct (#11881)

* fix: use .js extension for ESM imports of RoutePeerKind

The imports incorrectly used .ts extension which doesn't resolve
with moduleResolution: NodeNext. Changed to .js and added 'type'
import modifier.

* fix tsconfig

* refactor: unify peer kind to ChatType, rename dm to direct

- Replace RoutePeerKind with ChatType throughout codebase
- Change 'dm' literal values to 'direct' in routing/session keys
- Keep backward compat: normalizeChatType accepts 'dm' -> 'direct'
- Add ChatType export to plugin-sdk, deprecate RoutePeerKind
- Update session key parsing to accept both 'dm' and 'direct' markers
- Update all channel monitors and extensions to use ChatType

BREAKING CHANGE: Session keys now use 'direct' instead of 'dm'.
Existing 'dm' keys still work via backward compat layer.

* fix tests

* test: update session key expectations for dmdirect migration

- Fix test expectations to expect :direct: in generated output
- Add explicit backward compat test for normalizeChatType('dm')
- Keep input test data with :dm: keys to verify backward compat

* fix: accept legacy 'dm' in session key parsing for backward compat

getDmHistoryLimitFromSessionKey now accepts both :dm: and :direct:
to ensure old session keys continue to work correctly.

* test: add explicit backward compat tests for dmdirect migration

- session-key.test.ts: verify both :dm: and :direct: keys are valid
- getDmHistoryLimitFromSessionKey: verify both formats work

* feat: backward compat for resetByType.dm config key

* test: skip unix-path Nix tests on Windows

src/plugin-sdk/index.ts

@@ -118,6 +118,9 @@ export { ToolPolicySchema } from "../config/zod-schema.agent-runtime.js";
 export type { RuntimeEnv } from "../runtime.js";
 export type { WizardPrompter } from "../wizard/prompts.js";
 export { DEFAULT_ACCOUNT_ID, normalizeAccountId } from "../routing/session-key.js";
+export type { ChatType } from "../channels/chat-type.js";
+/** @deprecated Use ChatType instead */
+export type { RoutePeerKind } from "../routing/resolve-route.js";
 export { resolveAckReaction } from "../agents/identity.js";
 export type { ReplyPayload } from "../auto-reply/types.js";
 export type { ChunkMode } from "../auto-reply/chunk.js";