feat(terminal): add manual tab rename command and dialog

[niwo-gh]

Summary

• Adds a userTitle field to TerminalView.State that lets users manually rename terminal tabs
• Rename is accessible via the pane context menu ("Rename") and the command palette ("Rename Terminal")
• The manual title takes priority over OSC/shell-set titles and profile names; clearing it restores the previous automatic name
• Persists across sessions via the existing state serialization

Resolves #94

Changes

Area	Detail
State	New nullable userTitle: string | null field with fixTyped validation; defaults to null
UI	Rename item added to pane context menu (grouped with copy/edit/restart)
Command	rename-terminal registered via addCommand with withLastFocusedView ([false, true])
Dialog	DialogModal with text input; trims whitespace, converts empty to null
i18n	4 new keys in en locale (commands.rename-terminal, components.terminal.menus.rename, .rename-prompt, generic.rename); 3 icon keys in en/asset.json; all 48 non-English locales synced via sync-locale-keys.mjs
Tests	tests/src/terminal/view.spec.ts — covers State.DEFAULT, State.fix() with valid string, missing, non-string, boolean, null, and empty string inputs
Changeset	manual-tab-rename-minor.md — minor bump

How it works

1. User right-clicks a terminal tab → "Rename" (or invokes "Rename Terminal" from the command palette)
2. A dialog appears with a text input pre-filled with the current custom title (or empty if none)
3. On confirm, the trimmed value is stored as state.userTitle; empty input clears to null
4. The name getter priority chain: userTitle → OSC title → profile name → executable basename → i18n fallback
5. Setting this.state triggers updateView() which refreshes the tab header and persists layout

Testing

• 134 vitest tests pass (14 files), 0 type errors, 0 unhandled errors
• New test file mocks src/import.js to avoid xterm addon loading in the test environment