feat(site/src): redesign Alert to match the Coder kit spec - #30908

Restyles the shared Alert to match the Coder kit alert spec (Figma node 3613:569) and adds the two new kit variants: a single-line compact alert and an error-only "Technical details" disclosure.

ErrorAlert now fills that disclosure from the error itself: request ID (X-Coder-Request-Id), status, method and URL, the response Date header, and any response fields beyond message/detail (for example validations). Non-request errors show the stack trace. This replaces its two <details> blocks ("Response data", "Stack Trace").

API changes (all additive)

• compact?: boolean: one line, items centered, min height 54px. actions renders inline after the text and should be a single Link size="sm".
• details?: readonly AlertDetail[] ({ label, value }): rendered only for non-compact error alerts, collapsed by default, with a copy button that copies label: value lines.
• AlertDetail type export.
• ErrorAlert accepts an optional title for a user-facing outcome (for example "We couldn't create this workspace"), per the kit's "name the failure" guidance. With a title, the error's detail becomes the description and the raw API message moves to a "Message" row in Technical details. When there is no detail, the raw message stays as the description and gets no row. Without title, behavior is unchanged; no existing callers are migrated in this PR.
• mockApiError accepts optional request, status, statusText, headers.

Visual changes that affect existing callers

• Prominent success (and info) is removed, per the designer's decision. Alert has no prominent style for info/success; passing prominent with them renders the default style. The prop type is unchanged so dynamic callers still compile. Callers updated:
  • site/src/pages/TemplateVersionEditorPage/TemplateVersionEditor.tsx:309: the floating "published" success alert drops prominent and uses the default style (no green background).
  • site/src/pages/WorkspacePage/AgentAlert.stories.tsx: removed the InfoProminent story. AgentAlert still forwards prominent, but modules/workspaces/health.ts always passes prominent: false for info.
  • site/src/components/Alert/Alert.stories.tsx: removed the ProminentIgnoredForInfoAndSuccess story. No tests covered prominent success.
• Text is 12px/18px everywhere (previously 14px). AlertTitle is semibold (was medium) and AlertDescription is regular weight and display: block. This affects all 36 files that use AlertTitle/AlertDescription and all inline-text alerts. Two callers already override these: TemplateFilesPage.tsx:58 (font-semibold, now redundant) and RoleSelector.tsx:244-249 (font-normal).
• Error icon is OctagonXIcon (was CircleAlertIcon). Radius is rounded-md (was rounded-lg), and there is now a shadow-sm.
• ErrorAlert debug output (116 non-story files): the "Response data"/"Stack Trace" disclosures become one "Technical details" disclosure. Axios errors no longer show a JS stack trace, and response JSON leaves out the message/detail already shown in the alert, per the kit's alert pattern guidance. showDebugDetail={false} still hides it. Two page stories that clicked or checked the old labels are updated.

Apart from the prominent success caller above, I did not rewrite any callers.

Checks: pnpm lint (biome, oxlint, tsc, circular deps, compiler), full pnpm test, and pnpm test:storybook for the Alert, ErrorAlert, ChatSearchDialog, and SecretsPageView stories all pass. The frontend-deep-review findings are fixed. One remaining nit: SecretsPageView.stories.tsx:773 keeps a pre-existing play assertion, retargeted to the new label.

Generated by Coder Agents on behalf of @designertyler.