Add workspace-aware Codex chat history panel

[Hronom]

Summary

• add a dedicated Codex Chats Activity Bar panel backed by the local Codex session index
• open selected conversations as pinned official Codex editor tabs
• group chats for the current workspace first and place other workspaces in a separate collapsed section
• add automatic refresh, New Chat and Refresh actions, a new geometric icon, and local metadata caching
• release the feature as version 1.1.0

Why

Codex exposes conversations as editor tabs but did not provide a compact workspace-aware history panel comparable to other coding-agent extensions. This adds that navigation workflow without network requests or transcript parsing.

User impact

Users can open the Codex Chats Activity Bar view, see current-workspace chats first, expand chats from other workspaces, and click any item to reopen it in a pinned editor tab.

Validation

• npm ci
• npm test
• node scripts/check-release.mjs v1.1.0
• npm run package -- --out codex-extras-1.1.0.vsix
• verified the VSIX includes the runtime session index module and new sidebar icon
• verified all indexed local sessions resolve workspace metadata using only the metadata prefix