Run final manual QA matrix sweep (original Step 9)

[RE-codes]

Story

As a maintainer, before declaring MVP complete, I need a clean-vault walk through the full QA matrix in all three modes.

Tasks

• Set up a clean sandbox vault with only this plugin enabled.
• Walk all 12 rows of plan/gfm-fragment-links-plan.md § QA Matrix in Reading, Live Preview, and Source mode where applicable (≈30 manual checks total).
• Smoke-test with a real VS-Code-authored README containing a kebab-case TOC; confirm every TOC link lands correctly.
• Record pass/fail in a dated "Final MVP QA" section of plan/QA-log.md.
• Any failure → return to a TDD cycle: write a failing unit test in the appropriate file before fixing.

Acceptance Criteria

• 12 × 3 (≈30) QA rows recorded as pass in plan/QA-log.md.
• Real-doc smoke test passes.
• No outstanding fail rows.

References

• Parent epic: Epic: MVP Completion Gate #98
• plan/gfm-fragment-links-plan.md § Step 9
• plan/gfm-fragment-links-plan.md § QA Matrix