fix(aibridge): track Charm Crush client and session ID (#24630)

*Disclaimer: implemented by a Coder Agent using Claude Opus 4.6*

Porting https://github.com/coder/aibridge/pull/277 to coder/coder after
the [aibridge code move](https://github.com/coder/coder/pull/24190).

## Summary

Fixes client detection and session ID tracking for the [Charm
Crush](https://github.com/charmbracelet/crush) AI coding client.

## Changes

### Bug fix: User-Agent matching

The actual Crush user-agent is `Charm-Crush/{version}
(https://charm.land/crush)` (hyphenated), but `GuessClient` only checked
for `charm crush/` (space-separated). After lowercasing,
`Charm-Crush/0.2.0` becomes `charm-crush/0.2.0`, which did not match the
`charm crush/` prefix.

Now matches both formats for backwards compatibility.

### Session ID tracking

Adds an explicit `ClientCrush` case to `GuessSessionID`. Crush does not
currently send a session ID header to upstream AI providers, so this
returns `nil` (consistent with how `ClientZed`, `ClientRoo`, and
`ClientCursor` are handled).

### Tests

- Added `charm_crush_hyphen` test case for `GuessClient` using the real
user-agent format.
- Added `crush_returns_empty` test case for `GuessSessionID`.

aibridge/client.go

@@ -51,7 +51,7 @@ func GuessClient(r *http.Request) Client {
 		return ClientRoo
 	case strings.HasPrefix(userAgent, "coder-agents/"):
 		return ClientCoderAgents
-	case strings.HasPrefix(userAgent, "charm crush/"):
+	case strings.HasPrefix(userAgent, "charm crush/") || strings.HasPrefix(userAgent, "charm-crush/"):
 		return ClientCrush
 	case r.Header.Get("x-cursor-client-version") != "":
 		return ClientCursor

aibridge/client_test.go

@@ -79,10 +79,15 @@ func TestGuessClient(t *testing.T) {
 			wantClient: aibridge.ClientCoderAgents,
 		},
 		{
-			name:       "charm_crush",
+			name:       "charm_crush_space",
 			userAgent:  "Charm Crush/0.1.11",
 			wantClient: aibridge.ClientCrush,
 		},
+		{
+			name:       "charm_crush_hyphen",
+			userAgent:  "Charm-Crush/0.2.0 (https://charm.land/crush)",
+			wantClient: aibridge.ClientCrush,
+		},
 		{
 			name:       "cursor_x_cursor_client_version",
 			userAgent:  "connect-es/1.6.1",

aibridge/session.go

@@ -75,6 +75,8 @@ func GuessSessionID(client Client, r *http.Request) *string {
 		return cleanRef(r.Header.Get("X-KILOCODE-TASKID"))
 	case ClientCoderAgents:
 		return cleanRef(r.Header.Get("X-Coder-Chat-Id"))
+	case ClientCrush:
+		return nil // Crush does not send a session ID header.
 	case ClientRoo:
 		return nil // RooCode doesn't send a session ID.
 	case ClientCursor:

aibridge/session_test.go

@@ -182,6 +182,11 @@ func TestGuessSessionID(t *testing.T) {
 			name:   "coder_agents_without_chat_id",
 			client: aibridge.ClientCoderAgents,
 		},
+		// Crush.
+		{
+			name:   "crush_returns_empty",
+			client: aibridge.ClientCrush,
+		},
 		// Roo.
 		{
 			name:   "roo_returns_empty",