fix(extension): local content extraction for Chrome Web Store approval (#76)

* fix(extension): replace server API with local content extraction

Chrome Web Store rejected the extension because the core "Save page as
Skill" feature called https://skillkit.sh/api/save-skill which is
unreachable during review. This rewires page saving to work entirely
locally using chrome.scripting.executeScript to extract page content
(title, meta description, headings, body text) directly in the browser.

- Remove API_URL and callSaveApi() server dependency
- Add extractPageContent() via chrome.scripting.executeScript
- Add detectTags() with weighted keyword scoring (URL/headings/body)
- Add buildPageSkill() to generate SKILL.md with frontmatter locally
- Add scripting permission to manifest
- Pass tabId from popup to background for script injection targeting
- Block chrome-extension:// and chromewebstore.google.com URLs
- Add console.error logging in catch blocks for debuggability
- Guard currentTabId validity in popup click handler
- Update store listing to reflect fully local processing
- Bump version to 1.20.0

* fix(extension): address code review findings for robustness

- Extract RESTRICTED_PREFIXES and isRestricted() into shared constants.ts
  so popup and background use the same URL blocklist
- Fix yamlEscape to quote YAML bare scalars (true/false/null/yes/no/on/off)
  and numeric strings that parsers would coerce to non-string types
- Apply yamlEscape to skill name fields in both buildPageSkill and
  buildSelectionSkill to prevent YAML misinterpretation
- Switch tag detection from substring matching to word-boundary regex
  to eliminate false positives (e.g. "js" matching "adjustments")
- Check chrome.runtime.lastError in download callback and always
  revoke blob URL to prevent leaks on download failure

Author: rohitg00

packages/extension/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@skillkit/extension",
-  "version": "1.19.2",
+  "version": "1.20.0",
   "private": true,
   "description": "Chrome extension to save any webpage as an AI agent skill",
   "type": "module",