Story-2196: Audit log timestamp right alignment

The audit entry card previously rendered the timestamp under the action header, inside the content column. This story moves that timestamp to the card's inner right edge on wider screens while preserving the original stacked placement on small screens.

What changed

• src/components/settings/audit-log/audit-entry.tsx now renders the action header and timestamp as responsive flex siblings.
• At sm and above, the timestamp uses the row's available space to sit flush with the card's right padding and stay top-aligned with the header/action line.
• Below sm, the same timestamp falls back under the wrapped header content, so narrow cards avoid clipping, overlap, and horizontal scroll.
• AuditSnapshotView remains outside the header row, so diff, summary, file, run, and tombstone snapshots still span the full content width below the header.

Storybook coverage

Visual verification

• Storybook rendered at http://localhost:6007/; the four story iframe URLs above were captured with Playwright.
• Wide frame DOM measurements confirmed the timestamp right edge matched the card's inner right padding for both human and agent variants.
• Narrow frame DOM measurements confirmed the timestamp top followed the wrapped header cluster, with document and body scroll widths equal to the viewport width.

Verification

• pnpm lint — passed; one pre-existing no-img-element warning in src/components/add-matter/avatar.tsx.
• pnpm test — passed: 171 files, 1046 tests.
• pnpm build — passed.
• git diff --check — clean.
• UI scans: the repo-wide i18n/color scans only reported pre-existing literals/token definitions/issue-number false positives; targeted scans of the touched diff reported no hardcoded user-facing attributes and no color literals.