feat(tiktok): add TikTok as 7th signal source via Apify

Add TikTok search, scoring, and rendering using the Apify platform
(clockworks/tiktok-scraper actor). Users bring their own APIFY_API_TOKEN
($5/month free credits, no CC required). The shared apify_client_wrapper
module is designed for reuse by future Facebook/Instagram sources.

- New modules: tiktok.py (search + caption extraction), apify_client_wrapper.py
- Schema: TikTokItem dataclass, shares field on Engagement, Report.tiktok
- Pipeline: normalize → filter → score → sort → dedupe → cross-link → render
- Scoring: 0.50*log1p(views) + 0.30*log1p(likes) + 0.20*log1p(comments)
- SKILL.md bumped to v2.7 with TikTok stats, citations, and security docs
- 26 unit tests covering relevance, normalize, score, dedupe, render, round-trip

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/lib/ui.py

@@ -71,6 +71,12 @@ YOUTUBE_MESSAGES = [
     "Fetching transcripts...",
 ]
 
+TIKTOK_MESSAGES = [
+    "Searching TikTok for trending videos...",
+    "Finding what's viral on TikTok...",
+    "Scanning TikTok for relevant content...",
+]
+
 HN_MESSAGES = [
     "Searching Hacker News...",
     "Scanning HN front page stories...",
@@ -271,6 +277,15 @@ class ProgressDisplay:
         if self.spinner:
             self.spinner.stop(f"{Colors.RED}YouTube{Colors.RESET} Found {count} videos")
 
+    def start_tiktok(self):
+        msg = random.choice(TIKTOK_MESSAGES)
+        self.spinner = Spinner(f"{Colors.PURPLE}TikTok{Colors.RESET} {msg}", Colors.PURPLE, quiet=True)
+        self.spinner.start()
+
+    def end_tiktok(self, count: int):
+        if self.spinner:
+            self.spinner.stop(f"{Colors.PURPLE}TikTok{Colors.RESET} Found {count} videos")
+
     def start_hackernews(self):
         msg = random.choice(HN_MESSAGES)
         self.spinner = Spinner(f"{Colors.YELLOW}HN{Colors.RESET} {msg}", Colors.YELLOW, quiet=True)
@@ -298,7 +313,7 @@ class ProgressDisplay:
         if self.spinner:
             self.spinner.stop()
 
-    def show_complete(self, reddit_count: int, x_count: int, youtube_count: int = 0, hn_count: int = 0, pm_count: int = 0):
+    def show_complete(self, reddit_count: int, x_count: int, youtube_count: int = 0, hn_count: int = 0, pm_count: int = 0, tiktok_count: int = 0):
         elapsed = time.time() - self.start_time
         if IS_TTY:
             sys.stderr.write(f"\n{Colors.GREEN}{Colors.BOLD}✓ Research complete{Colors.RESET} ")
@@ -307,6 +322,8 @@ class ProgressDisplay:
             sys.stderr.write(f"{Colors.CYAN}X:{Colors.RESET} {x_count} posts")
             if youtube_count:
                 sys.stderr.write(f"  {Colors.RED}YouTube:{Colors.RESET} {youtube_count} videos")
+            if tiktok_count:
+                sys.stderr.write(f"  {Colors.PURPLE}TikTok:{Colors.RESET} {tiktok_count} videos")
             if hn_count:
                 sys.stderr.write(f"  {Colors.YELLOW}HN:{Colors.RESET} {hn_count} stories")
             if pm_count:
@@ -316,6 +333,8 @@ class ProgressDisplay:
             parts = [f"Reddit: {reddit_count} threads", f"X: {x_count} posts"]
             if youtube_count:
                 parts.append(f"YouTube: {youtube_count} videos")
+            if tiktok_count:
+                parts.append(f"TikTok: {tiktok_count} videos")
             if hn_count:
                 parts.append(f"HN: {hn_count} stories")
             if pm_count: