docs(getting-started): match real scan output verbatim

[cicdteam]

Summary

Three corrections to the First scan example so it matches actual output byte-for-byte:

1. Phase tracker glyph: ▶ (U+25B6) → ▸ (U+25B8), the actual character emitted by internal/progress/progress.go:127,142.
2. Re-add the 4th MEDIUM ... 0 0 ~0 row that the analyzer prints for the metric-level label-pattern finding. Dropping it in the previous PR made the table look unrealistically tidy.
3. Restore the full 5-trace-ID Sample: line; trimming it to 3 mid-paragraph IDs was an aesthetic choice the user (correctly) flagged as not matching real output.

Timings updated to a real recorded scan (118/8/13/7 ms).

Test plan

• mkdocs build --strict clean.
• CI green.
• Post-merge: https://remetric.dev/getting-started/#first-scan shows ▸ glyph + 4-row table + full sample.