feat(): codex parity with claude code session information

[StuBehan]

Summary

Brings Codex to parity with Claude Code for session info + notifications in StackNudge. Codex sessions now show live context-window usage in the Sessions tab (e.g. 26K · gpt-5.5) and get context-fill alerts, permission prompts surface the tool/command, and Codex is auto-wired by the shell installer to match the macOS first-launch wizard. Also fixes an installer venv crash and a build.sh source-list gap.

Changes

Codex context-window usage (Sessions tab)

• Add panel/CodexTranscriptStats.swift (CodexTranscriptReader) — parses Codex rollout JSONL (~/.codex/sessions/**/rollout-*.jsonl) token_count events. Context occupancy = last_token_usage.total_tokens − reasoning_output_tokens, matching Codex's own tokens_in_context_window() (cached input is a subset of input, never summed).
• TranscriptReader.read now dispatches by path: Codex rollouts → CodexTranscriptReader, everything else → the existing Claude reader. The event→stats→UI path is already agent-generic, so Codex sessions populate the same context row + context-fill alerts as Claude.

Installer / hooks

• install.sh + uninstall.sh: auto-wire/remove Codex (~/.codex/hooks.json, Claude-shaped Stop + PermissionRequest), matching what the macOS first-launch wizard already does.
• notify.sh: agent_supports_decision() gates the in-panel Allow button + blocking permission FIFO to agents whose hook can consume a decision (claude-code, codex). Gemini/Antigravity (observability-only Notification hooks) no longer create a pointless blocking FIFO or show a non-functional Allow button.
• notify.sh: permission banner resolves Codex's apply_patch tool to a filename (apply_patch: foo.ts) instead of a bare tool name.

Fixes

• install.sh: clear a partial/incompatible venv (rm -rf "$VENV") before python -m venv, so re-installs don't abort with [Errno 17] File exists.
• build.sh: add panel/CodexTranscriptStats.swift to the explicit swiftc source list (SPM globs it; the shipping build doesn't).

Docs / tests

• README.md: reconcile the support matrix + installer/wizard wording (add Antigravity, correct the Cursor-permission note).
• Tests/StackNudgePanelCoreTests/CodexTranscriptReaderTests.swift: XCTest covering occupancy math, latest-event selection, the cached/cumulative traps, nil cases, and path dispatch.

Testing

• swift build — clean (library incl. the new file).
• ./build.sh — succeeds (full shipping app).
• bash -n + shellcheck -S error — clean on install.sh, uninstall.sh, notify.sh, build.sh.
• Validated CodexTranscriptReader against a real Codex 0.136 rollout via a standalone swiftc harness → tokens=25864, model=gpt-5.5; plus XCTest fixtures (CI runs swift test under Xcode; can't run locally — CommandLineTools lacks XCTest).
• Manually verified on macOS: after make build + install, a live Codex session shows the context row (… · gpt-5.5) in the Sessions tab and fires context-fill alerts, identical to Claude.

Related issues

None.