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

extensions/tlon/src/targets.ts

@@ -1,5 +1,5 @@
 export type TlonTarget =
-  | { kind: "dm"; ship: string }
+  | { kind: "direct"; ship: string }
   | { kind: "group"; nest: string; hostShip: string; channelName: string };
 
 const SHIP_RE = /^~?[a-z-]+$/i;
@@ -32,7 +32,7 @@ export function parseTlonTarget(raw?: string | null): TlonTarget | null {
 
   const dmPrefix = withoutPrefix.match(/^dm[/:](.+)$/i);
   if (dmPrefix) {
-    return { kind: "dm", ship: normalizeShip(dmPrefix[1]) };
+    return { kind: "direct", ship: normalizeShip(dmPrefix[1]) };
   }
 
   const groupPrefix = withoutPrefix.match(/^(group|room)[/:](.+)$/i);
@@ -78,7 +78,7 @@ export function parseTlonTarget(raw?: string | null): TlonTarget | null {
   }
 
   if (SHIP_RE.test(withoutPrefix)) {
-    return { kind: "dm", ship: normalizeShip(withoutPrefix) };
+    return { kind: "direct", ship: normalizeShip(withoutPrefix) };
   }
 
   return null;