Enhance/timeline updates

[the-non-expert]

1. Added more granular copy options: Every H1 and H2 tag has a copy option now. Every H3 or smaller heading has a copy option if the prose text is more than 150 characters. Every code block has a copy option now.

2. Show written file content in Write tool modal - The Write tool's timeline card now shows the full content of the file that was written, with a scrollable container and a line count label. Previously it only showed the file path.

3. Show task subject in TaskUpdate modal - TaskUpdate timeline events now display the task's description text as a subtitle (e.g. "Fix the login bug") instead of just "Task #N". Required a pre-scan pass to parse TaskCreate result content to build a task ID → subject map.

4. Scroll position restore on back navigation - When you scroll down on the /sessions or /projects/[slug] route, click into a session, then press back — the page returns to exactly where you were. Uses beforeNavigate + sessionStorage + onMount + requestAnimationFrame, matching the existing pattern from /skills.

5. Last-opened session highlight - After pressing back from a session, the card you previously clicked glows with a 2px accent-colored ring that fades out over 1.8s. Lets you immediately see which session you were looking at.

6. Pagination state restore on back navigation - Going to page 3, clicking a session, and pressing back now returns you to page 3. For the sessions page (which uses client-side data fetching), the page number is saved to sessionStorage and restored via reloadSessions() on mount. Scroll restore is deferred until after the page data loads so it lands on the right content. For the project page (uses goto()), the URL sync effect now preserves ?page=n so SvelteKit's history state works correctly.

[the-non-expert]

7. Fixing Project scoped skills path mismatch - By intercepting navigation with onclick when projectEncodedName is present, allows users to drill down into project folders statelessly from the perspective of the router. gracefully falls back to real URL links (/skills?path=...) when on the global dashboard.