chore: rebrand companion-os to clanker-agent

- Rename all package names from companion-* to clanker-*
- Update npm scopes from @mariozechner to @harivansh-afk
- Rename config directories .companion -> .clanker
- Rename environment variables COMPANION_* -> CLANKER_*
- Update all documentation, README files, and install scripts
- Rename package directories (companion-channels, companion-grind, companion-teams)
- Update GitHub URLs to harivansh-afk/clanker-agent
- Preserve full git history from companion-cloud monorepo

packages/coding-agent/test/session-info-modified-timestamp.test.ts

@@ -47,7 +47,7 @@ describe("SessionInfo.modified", () => {
   });
 
   it("uses last user/assistant message timestamp instead of file mtime", async () => {
-    const filePath = join(tmpdir(), `companion-session-${Date.now()}-modified.jsonl`);
+    const filePath = join(tmpdir(), `clanker-session-${Date.now()}-modified.jsonl`);
     createSessionFile(filePath);
 
     const before = await stat(filePath);