feat(widgets): add Claude memory widget

[3351163616]

What

Adds a new claude-memory widget that surfaces the current project's Claude Code auto-memory state in the status line: how many memory files exist and how recently they were updated.

Renders 🧠 <count> (<age>), e.g. 🧠 5 (2h).

Why

Claude Code maintains per-project persistent memory under ~/.claude/projects/<slug>/memory/ (with a MEMORY.md index). Surfacing the count and last-updated age gives a quick at-a-glance signal of the current project's memory state — e.g. whether memory is fresh or has gone stale — without leaving the prompt.

Behavior

• Locates the memory directory next to the transcript: dirname(transcript_path)/memory (no project-slug computation needed).
• Count: .md files in the memory dir excluding the MEMORY.md index.
• Age: newest mtime across all .md files, formatted <1m / Xm / Xh / Xd.
• rawValue mode omits the icon prefix.
• Hidden (returns null) when there is no transcript path, the memory dir is missing, the count is 0, or any filesystem error occurs — the status line never throws.
• Category Session; default color magenta; supports colors and raw value; getNumericValue() returns the count.

Implementation

• Reads the filesystem synchronously inside render() (same pattern as FreeMemory); no RenderContext or entry-point changes.
• Covered by unit tests (ClaudeMemory.test.ts) with the fs module mocked.

Notes

Depends on Claude Code's memory directory convention (memory/ + MEMORY.md). If that convention shifts, the widget degrades gracefully (hides) rather than erroring.