fix(cli): ASCII glyph fallback for Windows console mojibake (#168) (#178)

The shimmer progress renderer writes from a worker thread via
`fs.writeSync(1, ...)` to keep the animation smooth while the main
thread is busy in SQLite. That path bypasses Node's TTY-aware
UTF-8->codepage conversion on Windows, so glyphs like `|`/`<>`/`-`
were emitted as raw UTF-8 bytes and reinterpreted by the console's
OEM codepage (CP437, CP936, ...), producing strings like
`鋍?[0m 鉒?[0m Scanning files 鈥?N found`.

Add `src/ui/glyphs.ts` with `supportsUnicode()` detection plus
matched Unicode + ASCII glyph sets, and route all CLI/shimmer
output through `getGlyphs()`. Defaults: ASCII on Windows and on
Linux kernel consoles (`TERM=linux`), Unicode everywhere else.
`CODEGRAPH_UNICODE=1` and `CODEGRAPH_ASCII=1` are escape hatches.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>