Editor: fix Buffer Carousel, split diff, and AI selector issues

[Finesssee]

Summary

This PR now reflects the full set of fixes carried on this branch, including the original CROF/editor cleanup items plus the AI provider/model selector follow-up.

What changed

• Buffer Carousel
  • made the setting easier to discover with a visible Learn more help chip
  • improved carousel centering so it only scrolls when the target card is actually out of view
  • added a new Focus Buffer on Hover setting, defaulting to off
  • dim inactive carousel cards so the active buffer is easier to pick out
  • expanded Settings search terms for the carousel options
• Embedded web viewer on Linux
  • switched Linux embedded webviews to a child-webview path built with wry
  • moved creation, resize, visibility, zoom, metadata, and shortcut polling onto the Linux embedded path
  • updated the frontend bounds/visibility sync so embedded pages stay aligned with their container and avoid flicker when switching buffers
• AI settings and chat flow
  • fixed the provider/model selector positioning inside the settings dialog
  • made the selector roomier and kept its dropdown constrained to the dialog instead of the full viewport
  • kept provider and model changes in sync when selecting a model from another provider
  • prevented stale dynamic-model refreshes from overwriting the current selection
  • cleaned up ACP thinking-state rendering so long-running thought activity updates in place instead of duplicating rows
  • excluded agent buffers from saved/restored chat context selection
  • opening the agent from the empty editor state now starts a fresh chat first
• LSP startup reporting
  • surfaced startup failures more clearly in the editor-side reporting flow
  • fixed JS language-server detection when the installed server is a symlinked bin wrapper, which fixes the RPM/Linux launch case
• Git split diff and status panel
  • fixed split diff spacer rendering so hidden-side rows get the right muted gutter/background treatment
  • corrected split diff line-number mapping for context lines
  • split the status panel into clearer Staged, Unstaged, and Untracked sections with counts
  • fixed optimistic stage/unstage state so files that appear in both staged and unstaged groups do not collapse into the wrong row state
• Markdown viewer
  • fixed ordered lists so numbering survives blank lines instead of restarting
  • loosened heading spacing so rendered markdown is easier to scan
• Terminal and shortcuts
  • made terminal launch commands reliable by waiting for real shell output before dispatching the initial command, with a fallback timer if the shell stays silent
  • wired create-terminal-with-command through the same initial-command path
  • restored sidebar navigation shortcuts for Show Files and Show Git
  • added support for cmd+shift+= alongside cmd+= for zoom in
  • gave terminal zoom-out finer intermediate steps without changing editor zoom behavior
• Misc
  • ignored local .pi/ and .tmp/ scratch directories

Test coverage

• added regression tests for:
  • AI ACP event timeline updates
  • chat context buffer eligibility
  • LSP startup reporting
  • markdown ordered-list parsing
  • split diff marking and status-panel optimistic staging
  • AI provider/model selection
  • terminal initial-command dispatch
  • zoom-store behavior

Notes

• This description replaces the earlier partial-scope note. The body now matches the work that is actually present in this PR branch.