feat(extension): add human-readable browser instance names

[imnemo]

Refs #219. Complements #298.

Problem

bsk browsers already exposes a label and session selection already accepts --browser <id-or-label>, but the extension popup does not provide a way to set that label. With multiple connected profiles, users therefore have to map opaque instance IDs to browser profiles before every task.

Changes

• Add a compact Browser name editor to the extension popup, with explicit save, Enter/Escape keyboard behavior, trimming, clearing, and a 48-character limit.
• Prevent labels that look like an 8-character instance ID, avoiding selector precedence surprises.
• Reconnect after a persisted label change so the daemon registry sees the new name immediately. The popup explains that saving ends active tasks in that browser.
• Preserve instance IDs as the canonical fallback and keep duplicate-label handling fail-closed in the daemon.
• Add English, Simplified Chinese, and Korean copy, plus profile-selection documentation and CLI examples.

No protocol changes or new browser permissions are required. Automatic Chrome profile discovery remains out of scope; users still choose the mapping in the profile where the extension is installed.

Validation

• Extension test suite: 1,882 passed / 103 skipped
• Focused popup and connection lifecycle tests: 58 passed
• Localization tests: 52 passed
• Extension TypeScript compilation: passed
• Production extension build: passed
• Biome and Stylelint: passed
• Manual popup review at the shipped 320–340 px width: default, valid-name, and instance-ID-shaped validation states checked

pnpm lint currently reaches the DSH plugin suite and then fails on the existing prompt-size assertion (8,133 < 8,000). The same failure is present on upstream main at 0225683 and in its CI run; this change does not touch the DSH plugin or generated skill content.