feat: Firefox selection translation extension with local Ollama (initial version)

Implement the complete initial version of a Firefox WebExtension (Manifest V3)
that translates selected text on web pages using a local Ollama LLM and shows
the result in a small popover near the selection.

Specification alignment (Phase 0)
- Unified Specifications.md / Design.md / Security.md on the same approach:
  Ollama REST API + Fetch API + NDJSON streaming (no ollama-js SDK dependency)
- Fixed host_permissions to http://localhost/* and http://127.0.0.1/* because
  Firefox match patterns do not support port numbers (bug 1362809/1468162);
  the actual connection target is restricted to localhost/127.0.0.1 + any port
  by application-side validation (defense in depth, OLL-09)
- Clipboard: use navigator.clipboard.writeText() only inside the copy button
  click (user activation); no deprecated execCommand fallback

Implementation (zero dependencies, vanilla JS, no npm/Node required)
- manifest.json: MV3, background.scripts + type:module (event page, no
  service_worker), action popup, options_ui, content_scripts for http/https,
  permissions: storage + localhost host permissions only
- src/shared: constants (ports, limits, presets, error codes), message
  validation, settings schema (defaults / merge / sanitize / buildOptions /
  toApiThinking), system prompt builder (fixed prompt first + user prompt)
- src/background: message-router (runtime.Port streaming + runtime.onMessage
  for model list), translation-session (single active request, abort previous
  on new request, stale chunk suppression), ollama-client (fetch against
  /api/tags and /api/chat with buffering NDJSON line parser tolerant to chunk
  boundaries inside JSON objects, AbortController, host re-validation before
  every request, HTTP status to error-code mapping), settings-service
  (storage.local load/save with validation and fallback to defaults)
- src/content/content.js: single classic script (Firefox does not support ES
  modules in content scripts) with selection detection (selectionchange +
  mouseup + keyup, debounced), Shadow DOM action button, Shadow DOM popover
  with HIDDEN/LOADING/STREAMING/COMPLETED/ERROR state machine, port client
  with requestId-based stale chunk filtering, enabled-state sync via
  storage.onChanged; all dynamic text rendered via textContent only
- src/popup + src/options: full settings UI (enable toggle, Ollama host,
  model list from Ollama with saved-model warning, target language, thinking
  mode, temperature slider 0.0-2.0 step 0.1, context length presets
  4k/8k/16k/32k/128k/256k, seed random/fixed with integer value, user system
  prompt, advanced numeric options with steppers, stop sequences textarea)
- icons generated by tools/make-icons.ps1 (System.Drawing, no external tools)
- build.ps1 packages manifest.json + icons/ + src/ into dist zip, excluding
  tests/, doc/, ollama-js/ and tools/

Tests (71 passed, 0 failed)
- In-browser test runner (tests/test.html) with custom describe/it/assert
  framework; no npm, no Node.js
- Unit: constants sync between content mirror and shared module, Ollama host
  validation (localhost/127.0.0.1 + any port only; rejects external hosts,
  LAN IPs, https, credentials, paths), settings schema defaults and fallback,
  temperature 0.1-step validation, context length presets, seed modes,
  advanced option types, buildOptions omission of unset values and absence of
  tfs_z/mirostat fields, system prompt composition order, message validation
  with selection length boundary values
- Integration: NDJSON streaming across awkward byte boundaries, thinking
  chunk forwarding, malformed line tolerance, error payload mapping, think/
  options inclusion rules, model list, TranslationSession abort semantics,
  settings round-trip with storage.onChanged cache refresh, full port flow
  (started/chunk/completed), newer request aborts older with stale chunk
  discard, malformed message rejection, OLLAMA_UNAVAILABLE and
  INVALID_SETTINGS error paths, untrusted sender rejection

Security audit (Design.md section 24 checklist: all pass)
- No innerHTML/outerHTML/document.write/eval/new Function/localStorage
- No remote JS/CSS/fonts/CDN resources; no inline scripts in extension pages
- Ollama access limited to background; content scripts never fetch Ollama
- Background validates message type/length/requestId; single concurrent
  translation enforced
- Clipboard API only (no execCommand fallback)
- Minimal permissions: storage + localhost host permissions

Docs
- README.md with build/load/usage instructions, API list, permission rationale
- doc/Testing-Results.md with automated test results, security audit results,
  and a 14-item manual Firefox verification checklist (to be executed on a
  real Firefox + Ollama environment)

1 files changed, 126 insertions, 0 deletions

diff --git a/tests/mocks.js b/tests/mocks.js
new file mode 100644
index 0000000..d8b9918
--- /dev/null
+++ b/tests/mocks.js
@@ -0,0 +1,126 @@
+/**
+ * Test mocks: fetch (NDJSON stream with controllable chunk boundaries),
+ * browser storage, and browser runtime port.
+ */
+(() => {
+  'use strict';
+
+  /**
+   * Create a Response whose body streams the given NDJSON lines, split into
+   * arbitrary byte chunks (to test JSON-boundary tolerance).
+   * @param {string[]} lines NDJSON lines
+   * @param {number[]} [chunkSizes] byte sizes per chunk (cycled)
+   * @returns {Response}
+   */
+  function ndjsonResponse(lines, chunkSizes) {
+    const text = lines.join('\n') + '\n';
+    const bytes = new TextEncoder().encode(text);
+    const sizes = chunkSizes && chunkSizes.length ? chunkSizes : [bytes.length];
+    let offset = 0;
+    let index = 0;
+    const stream = new ReadableStream({
+      pull(controller) {
+        if (offset >= bytes.length) {
+          controller.close();
+          return;
+        }
+        const size = sizes[index % sizes.length];
+        index++;
+        const end = Math.min(offset + size, bytes.length);
+        controller.enqueue(bytes.slice(offset, end));
+        offset = end;
+      }
+    });
+    return new Response(stream, { status: 200, headers: { 'Content-Type': 'application/x-ndjson' } });
+  }
+
+  /**
+   * @param {number} status
+   * @returns {Response}
+   */
+  function errorResponse(status) {
+    return new Response(JSON.stringify({ error: 'boom' }), { status, headers: { 'Content-Type': 'application/json' } });
+  }
+
+  /**
+   * Fake browser.storage.local backed by a Map.
+   * @returns {object} browser-like API
+   */
+  function fakeStorage() {
+    const data = new Map();
+    const listeners = [];
+    const local = {
+      async get(defaults) {
+        const result = {};
+        for (const key of Object.keys(defaults)) {
+          result[key] = data.has(key) ? data.get(key) : defaults[key];
+        }
+        return result;
+      },
+      async set(obj) {
+        const changes = {};
+        for (const [key, value] of Object.entries(obj)) {
+          changes[key] = { oldValue: data.get(key), newValue: value };
+          data.set(key, value);
+        }
+        for (const listener of listeners) listener(changes, 'local');
+      }
+    };
+    return {
+      local,
+      onChanged: {
+        addListener(fn) {
+          listeners.push(fn);
+        }
+      }
+    };
+  }
+
+  /**
+   * Fake runtime.Port with a message queue.
+   */
+  function fakePort() {
+    const listeners = { message: [], disconnect: [] };
+    return {
+      name: 'translation-stream',
+      sender: { id: 'test-extension' },
+      postMessage: () => {},
+      onMessage: {
+        addListener: (fn) => listeners.message.push(fn)
+      },
+      onDisconnect: {
+        addListener: (fn) => listeners.disconnect.push(fn)
+      },
+      __emit(message) {
+        for (const fn of listeners.message) fn(message);
+      },
+      __emitDisconnect() {
+        for (const fn of listeners.disconnect) fn();
+      }
+    };
+  }
+
+  /**
+   * Fake browser.runtime sufficient for message-router tests.
+   */
+  function fakeRuntime() {
+    const connectListeners = [];
+    const messageListeners = [];
+    return {
+      onConnect: {
+        addListener: (fn) => connectListeners.push(fn),
+        __emit(port) {
+          for (const fn of connectListeners) fn(port);
+        }
+      },
+      onMessage: {
+        addListener: (fn) => messageListeners.push(fn),
+        __listener() {
+          return messageListeners[messageListeners.length - 1];
+        }
+      }
+    };
+  }
+
+  window.TestMocks = { ndjsonResponse, errorResponse, fakeStorage, fakePort, fakeRuntime };
+})();
\ No newline at end of file