feat: add explicit comment resolution

[quantk]

What changed

• add explicit open/resolved state for saved human comments
• keep F7 limited to open comments without changing their state
• keep detached open comments visible after agent edits
• place detached comments beneath a unique exact former text match, including deleted lines
• make detached cards navigable with j/k and actionable with e, x, and d d
• document the workflow in README and agent-guide.md

Why

F7 inserts an unsubmitted draft, so treating insertion as delivery would lose feedback if the user never sends it. At the same time, old comments must not be resent forever. Explicit resolution lets the reviewer decide when feedback is complete while retaining comment history.

Validation

• npm run version:check
• npm test (42 Node tests, 12 Bun UI tests)
• npm run check