fix(page-title): wrap long page titles instead of clipping them

[Yi-111-a]

Fixes #68

Problem

The page title field is a single-line <input> (aria-label="Page title"), so a long title is clipped at the right edge instead of wrapping. For example "AI Coworkers: OpenAI Dots vs Meta Muse vs OpenDots" shows as "AI Coworkers: OpenAI Dots vs Meta Mus" in a ~1300 px window.

Fix

Render the title as a wrapping, auto-growing <textarea> instead of a single-line <input>:

• The field wraps (white-space: pre-wrap; overflow-wrap: break-word) and grows to fit every line, so no title is clipped horizontally.
• rows={1} plus a content-height effect (and field-sizing: content where supported) keep it exactly one line tall until the text actually wraps.
• Because a title is a single paragraph, Enter leaves the field; Shift+Enter still inserts a line break for the rare case a break is wanted.

The existing aria-label, placeholder, maxLength and the autosave path (controller.edit({ title })) are unchanged.

Verification

• New regression tests in tests/page-document-title.test.tsx cover the element type/props and the Enter vs Shift+Enter handling.
• vitest: my two new tests pass. The 7 pre-existing failures in the suite are unrelated — they come from node:sqlite requiring Node >=22 while this environment runs Node 20, and they fail identically on the unmodified tree.
• tsc --noEmit, eslint and prettier --check are clean on the changed files.