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/gateway-session-titles.test.ts

@@ -12,7 +12,7 @@ function createMockSession(options?: { sessionName?: string }) {
     dispose: vi.fn(),
     subscribe: vi.fn(() => () => {}),
     sessionManager: {
-      getSessionDir: () => "/tmp/companion-gateway-test",
+      getSessionDir: () => "/tmp/clanker-gateway-test",
       appendSessionInfo: vi.fn(),
       appendLabelChange: vi.fn(),
     },