feat: review model changes since the last approval

[damusix]

When an AI edits a model, serve now shows what changed since the last approval, and whether the agent explained it.

• Graph and flow diagrams: pulsing glows (green added, amber changed; unexplained alternates with red). Removed entities stay as faded ghosts with a red ✕. Edges glow along the line.
• Process Flows index and level menus: changed rows glow; rows with changes below them carry a dot.
• Dictionary: badges and column markers; removed items in warning red.
• Changes panel: the agent's notes, unexplained changes, and names a note claims but didn't change. Approve accepts the current state.
• Baseline and notes live in <model>/.ignatius/, ignored by a .gitignore next to ignatius.yml. Works without git. ignatius approve from the CLI.
• The modeling skill writes one change note per edit session, listing columns.

Also fixes modals sitting under the global findings banner (a tall modal's close button was unclickable). Main's CI now fails test-graph-bundle-mode on this; the fix is here so this PR can go green.

Contract: docs/spec/model-change-review.md. Guide: docs/guides/change-review.md. Checks need bun run build:cli before bun run test.