Restyle in-app toasts to match shadcn design language

[Ziinc]

Replace the solid saturated-color toast backgrounds (bg-destructive,
bg-primary, bg-green-600, bg-orange-600) with the app's shared shadcn
surface treatment: bg-popover, border, shadow-lg, rounded-lg. Each
toast type is now distinguished by a colored lucide icon and subtle
border tint instead of a full-color fill, matching Card/Dialog/Popover.
Add a toast-styles screenshot spec covering all four toast types in
light and dark mode, and update existing screenshot spec expectations
that described the old "green toast" look.

[github-actions]

📸 App QA screenshots

Re-ran the 4 flows whose spec this PR adds or modifies — 9 captures. Other specs in the library were not run.

⬇️ Download the screenshots

commits-tab-after-push

• commits-tab-after-push-01-before-push.png
  • The Commits tab is active and shows a 'Today' section with Workspace commit 2 above Workspace commit 1.
  • A 'Recent on ' section below lists 5 repo commits (Repo commit 1..5) plus the Initial commit, each tagged Immutable.
  • The header shows a blue 'Push to remote' button (workspace not yet pushed).
• commits-tab-after-push-02-after-push.png
  • The 'Push to remote' button is gone from the header (only 'Merge...' and the overflow menu remain).
  • A toast in the bottom-left corner with a green check icon reads 'Pushed to remote' / 'Changes pushed successfully'.
  • Workspace commit 1 and Workspace commit 2 are still listed, unchanged from the before-push screenshot.

header-sync-indicator-after-commit

• header-sync-indicator-01-before-commit.png
  • The Review tab is active and the diff pane shows sync-indicator.txt with one added line highlighted green.
  • The header (top bar, showing the feat/sync-indicator branch) has NO sync control at all -- the workspace is level with the remote, so neither a '↑'/'↓' counter nor the circular refresh-arrows icon is drawn; only the green 'Merge...' button and the overflow menu sit at the right edge.
  • A commit message box with placeholder 'Message' and a 'Commit' button are visible in the left file sidebar.
• header-sync-indicator-02-after-commit.png
  • The header now shows an '↑1' sync indicator with the circular refresh-arrows icon, just left of the green 'Merge...' button -- it appeared without navigating away from this workspace.
  • A 'Commit created' toast with a green check icon is visible in the bottom-left corner.
  • The Review tab's left sidebar no longer has a 'Changes' section; sync-indicator.txt now sits under 'Committed', tagged 'A'.

sync-after-commit

• sync-after-commit-01-before-sync.png
  • The Commits tab is active and lists 'Commit that must survive sync' as the newest workspace commit.
  • The header shows the feat/sync-after-commit branch and a sync control reading '↑1' (one commit ahead of remote).
  • synced.txt is not shown as an uncommitted current change — it is committed.
• sync-after-commit-02-after-sync.png
  • 'Commit that must survive sync' is still listed in the Commits tab, in the same position as the before screenshot.
  • A toast in the bottom-left with a green check icon reads 'Synced with remote' / 'Fetched and pushed changes'.
  • The '↑1' ahead indicator is gone from the header — the workspace is now in sync with the remote.
  • No empty '(no description set)' commit appears above the real commit.
• sync-after-commit-03-review-after-sync.png
  • The Review tab is active and synced.txt appears only under a 'Committed' section.
  • There is no 'Changes' section — synced.txt has not reverted to being an uncommitted current change.

toast-styles

• toast-styles-01-all-types.png
  • Four stacked toasts are visible in the bottom-left corner of the page.
  • Every toast shares the same neutral card-like surface (light background, subtle border, drop shadow, rounded corners) rather than a solid saturated color fill.
  • The 'Synced with remote' toast shows a green circular check icon on its left.
  • The 'Push failed' toast shows a red/destructive circular X icon on its left.
  • The 'Uncommitted changes' toast shows an orange triangle warning icon on its left.
  • The 'Terminal Restarting' toast shows a blue/primary-colored info icon on its left.
  • Each toast has a bold title line and a smaller, muted-colored description line below it.
  • Each toast has a small close (X) button on its right edge.
• toast-styles-02-all-types-dark.png
  • The page background is dark (dark mode is active).
  • Four stacked toasts are visible in the bottom-left corner, using a dark neutral surface consistent with the rest of the dark-mode UI, not a solid saturated color fill.
  • The 'Synced with remote' toast shows a green check icon.
  • The 'Push failed' toast shows a red/destructive X icon.
  • The 'Uncommitted changes' toast shows an orange triangle warning icon.
  • The 'Terminal Restarting' toast shows a blue/primary info icon.
  • Toast title and description text is legible against the dark background.

Each bullet under a capture is what the spec claims that image should show — open the PNG and check it.

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_{commit d67213c · workflow run — this comment is updated in place on each run.}