feat: PDF Viewer translation via context menu and two-mode Action Popupv0.1.0

Add Firefox built-in PDF Viewer support using only public WebExtensions
APIs: a selection context menu ("選択したテキストを翻訳") starts a
translation and the toolbar Action Popup shows the streaming result.
No content-script injection into the privileged PDF Viewer, no PDF.js
internals, no separate windows, no custom viewer (Specifications.md §4.6).

Specification alignment (Phase 1)
- Specifications.md: new requirements PDF-01..04 (PDF selection
  translation), CTX-01..03 (context menu translation), POP-01..06
  (popup two modes); SEL-06 updated to route PDF through the menus API;
  section 13.4 adds a 14-item manual PDF verification checklist; section
  15 removes "Firefox内蔵PDF Viewerへの対応" from out-of-scope
- Design.md: architecture diagram with the menus path, menu-translation
  component, menus permission, popup translation-result state machine
  (idle/starting/streaming/completed/error/cancelled), shared translation
  state (§9.2), context-menu integration phase, test plan and API audit
  checklist items (menus permission scope, no PDF Viewer internals)
- Security.md: menus permission restricted to selection-context
  translation; PDF Viewer treated as privileged browser UI (no injection,
  no wrappedJSObject/cloneInto/exportFunction, no internal DOM access);
  menus.OnClickData.selectionText treated as untrusted input passing the
  same validation pipeline; popup result rendering stays textContent-only

Background (Phase 2)
- translation-service.js (new): the single translation pipeline shared by
  every entry point - selection validation (type/trim/empty/control
  chars/max length), prompt building, Ollama request, session/abort, and
  the shared translation state (requestId, sourceText, translatedText,
  status, model, error, startedAt, source). "source" is metadata only; a
  PDF-specific translation engine does not exist
- menu-translation.js (new): validates menus.OnClickData.selectionText
  and starts a sink-less translation observed via GET_POPUP_STATE
- message-router.js: routes port translations through the shared service;
  new runtime messages GET_POPUP_STATE and REGENERATE_LAST; popup-state
  port handler broadcasts live state (initial push + every chunk/status
  change) so an open popup shows streaming progress in real time
- index.js: registers the selection context menu (contexts: ["selection"]
  only, no menus.onShown) and calls browser.action.openPopup()
  synchronously inside the click user gesture, catching failures so a
  popup-open problem never breaks the translation itself
- manifest.json: permissions now ["storage", "menus"]
- settings-service.js: __resetCacheForTests hook for test isolation

Popup two-mode UI (Phase 3)
- popup.html/js/css: mode nav (設定 / 翻訳). Translation mode shows
  status, model, streaming text (textContent only), user-safe error, and
  copy (Clipboard API only, no execCommand fallback), regenerate (new
  requestId reusing the stored source text) and a settings shortcut.
  Closing the popup never cancels the request; reopening shows the
  latest text and continues receiving chunks live. Initial mode: active
  (starting/streaming) translation wins, otherwise the last tab the user
  picked is restored (storage.local.popupMode, default settings)

Fresh-install model auto-selection
- translation-service.js ensureModelConfigured(): when storage.model is
  empty, pick the first model from the running Ollama and persist it
  before translating, mirroring the popup/options auto-select. A user who
  never opened any settings UI can translate immediately; when Ollama is
  unreachable a clear OLLAMA_UNAVAILABLE message is shown

User-safe error details
- detailForUser(): strips URLs (no internal host names echoed to the UI),
  caps length at 120 chars, drops full JSON response bodies, and hides
  meaningless low-level network errors so the popover/popup shows the
  base message plus at most a short, safe detail

Tests: 85 passed, 0 failed
- selectionText validation (untrusted input pipeline)
- menu selection -> translation -> popup state streaming/completed
- empty selection rejected without starting a request
- streaming status transitions observed through GET_POPUP_STATE
- Ollama unreachable surfaces a user-safe error into popup state
- newer request replaces older state (abort semantics)
- regenerateLast reuses source text with a fresh requestId
- popup-state port receives live broadcasts; wrong port names ignored
- fresh-install auto-select persists the first Ollama model
- error detail sanitization (URL stripping, length cap, JSON drop)
- popup/options smoke tests updated for the two-mode markup
- setupRouter resets the shared settings cache for test isolation

Docs: README documents the two-mode popup and PDF flow; Testing-Results
records automated results and the manual PDF checklist (to be executed).

No git-side surprises: this commit was created explicitly on request
(requirement 18 of the PDF task had deferred commits until now).

1 files changed, 39 insertions, 17 deletions

diff --git a/src/popup/popup.html b/src/popup/popup.html
index e51475f..06a4cf4 100644
--- a/src/popup/popup.html
+++ b/src/popup/popup.html
@@ -6,28 +6,50 @@
 </head>
 <body>
   <main>
-    <h1>Ollama Translations</h1>
+    <header class="popup-header">
+      <h1>Ollama Translations</h1>
+      <nav class="mode-nav" aria-label="表示切替">
+        <button id="nav-settings" type="button" class="nav-btn active" aria-pressed="true">設定</button>
+        <button id="nav-translation" type="button" class="nav-btn" aria-pressed="false">翻訳</button>
+      </nav>
+    </header>
 
-    <section class="row toggle-row">
-      <label class="toggle-label" for="enabled-toggle">翻訳機能</label>
-      <input type="checkbox" id="enabled-toggle" role="switch">
-    </section>
-
-    <section class="row">
-      <label for="model-select">モデル</label>
-      <div class="model-row">
-        <select id="model-select"></select>
-        <button id="reload-models" type="button" title="モデル一覧を再取得">↻</button>
+    <!-- Translation result mode -->
+    <section id="translation-mode" class="mode" hidden>
+      <p id="translation-status" class="status"></p>
+      <p id="translation-meta" class="meta" hidden></p>
+      <div id="translation-text" class="translation-text" aria-live="polite"></div>
+      <p id="translation-error" class="status error" hidden></p>
+      <div class="actions">
+        <button id="copy-translation" type="button" disabled>コピー</button>
+        <button id="regenerate-translation" type="button" disabled>再生成</button>
+        <button id="open-options-from-translation" type="button">設定を開く</button>
       </div>
-      <p id="model-status" class="status" hidden></p>
     </section>
 
-    <section class="row">
-      <label for="language-select">翻訳先言語</label>
-      <select id="language-select"></select>
-    </section>
+    <!-- Settings mode -->
+    <section id="settings-mode" class="mode">
+      <section class="row toggle-row">
+        <label class="toggle-label" for="enabled-toggle">翻訳機能</label>
+        <input type="checkbox" id="enabled-toggle" role="switch">
+      </section>
 
-    <button id="open-options" type="button">詳細設定を開く</button>
+      <section class="row">
+        <label for="model-select">モデル</label>
+        <div class="model-row">
+          <select id="model-select"></select>
+          <button id="reload-models" type="button" title="モデル一覧を再取得">↻</button>
+        </div>
+        <p id="model-status" class="status" hidden></p>
+      </section>
+
+      <section class="row">
+        <label for="language-select">翻訳先言語</label>
+        <select id="language-select"></select>
+      </section>
+
+      <button id="open-options" type="button">詳細設定を開く</button>
+    </section>
   </main>
   <script type="module" src="popup.js"></script>
 </body>