fix(sources): align SC source gating between code and docs

Two related drifts surfaced while reviewing PR #399 (EXCLUDE_SOURCES) —
docs claimed several SC-backed sources required INCLUDE_SOURCES opt-in
that the code didn't actually enforce, and threads was inconsistently
gated relative to its same-key siblings.

This commit picks the "code as source of truth + EXCLUDE_SOURCES as
suppression knob" model and aligns docs to match. It also promotes
threads to the same auto-on tier as tiktok and instagram, since all
three share the SC key and per-call cost shape — there was no real
product reason for threads being opt-in while the other two weren't.

The resulting source-gating model is three-tier and intentional:

  • **Auto-on if backing infra present** (suppress via EXCLUDE_SOURCES):
    reddit, HN, polymarket, X, youtube, github, bluesky, truthsocial,
    grounding, **tiktok, instagram, threads**

  • **INCLUDE_SOURCES persistent opt-in** (cost/billing reasons):
    perplexity (different paid API — OpenRouter),
    tiktok_comments / youtube_comments (N× extra SC calls per video)

  • **--search per-query opt-in** (relevance reasons):
    pinterest (visual pins, narrow utility),
    xiaohongshu (Chinese-market specific)

Changes:

- env.py: `is_threads_available()` drops the INCLUDE_SOURCES check,
  now mirrors tiktok/instagram (SC key → True). Docstring updated.
- tests/test_env_v3.py: new `ThreadsAvailabilityTests` class locks in
  the new contract and includes a regression guard ("INCLUDE_SOURCES
  should not be needed").
- SKILL.md: lines 333-338 rewritten so the model's "Build
  ACTIVE_SOURCES_LIST" checklist reflects what the engine actually
  runs. Drops false INCLUDE_SOURCES requirement for
  tiktok/instagram/threads; corrects pinterest to mention --search;
  adds missing INCLUDE_SOURCES=perplexity requirement.
- README: same alignment for the user-facing "Everything else in v3"
  section.

Note on EXCLUDE_SOURCES references in the new docs: the suppression
flag is wired up in PR #399. SKILL.md and README mention EXCLUDE_SOURCES
as the opt-out path; that prose is forward-looking until #399 lands.
The behavior changes in this PR (threads auto-on) are self-contained
and don't require #399 to function — but for users who want to suppress
the newly-auto-on threads source, #399 needs to land first.

README.md

@@ -152,8 +152,10 @@ Say "eli5 on" after any research run. The synthesis rewrites in plain language.
 
 - **Free Reddit comments.** Public JSON gives you threads + top comments with upvote counts. No API key, no ScrapeCreators. Just works.
 - **YouTube transcripts that actually work.** Widened candidate pool 3x past music videos to reach talk/review content with captions.
-- **Threads, Pinterest, YouTube + TikTok comments.** Opt-in sources via ScrapeCreators. Set `INCLUDE_SOURCES=tiktok,instagram` and add threads, pinterest, youtube_comments, tiktok_comments for more. `youtube_comments` and `tiktok_comments` surface top comments with vote counts the same way Reddit does.
+- **TikTok, Instagram, Threads.** All three activate automatically once `SCRAPECREATORS_API_KEY` is set — same key, same per-call cost. Suppress any of them with `EXCLUDE_SOURCES=tiktok,instagram,threads` (any comma-separated subset).
-- **Perplexity Sonar.** Grounded web search with citations via OpenRouter. Add `OPENROUTER_API_KEY` to unlock.
+- **Pinterest.** Per-query opt-in (visual pins, narrow utility): the model passes `--search=pinterest` for the runs that need it. Requires `SCRAPECREATORS_API_KEY`.
+- **YouTube + TikTok comments.** Persistent opt-in via `INCLUDE_SOURCES=youtube_comments,tiktok_comments` because each video pulls N extra ScrapeCreators calls on top of the base search. Surface top comments with vote counts the same way Reddit does.
+- **Perplexity Sonar.** Grounded web search with citations via OpenRouter. Add `OPENROUTER_API_KEY` and `INCLUDE_SOURCES=perplexity` (it's a separate paid API — opt-in keeps you from being surprise-billed).
 - **Polymarket noise filtering.** Common-word disambiguation prevents "Apple" from matching "Will Apple release a car?"
 - **Resilient Reddit.** Timeout budgets and runtime fallback. One slow thread doesn't kill the whole run.
 - **Fun judge v2.** Humor scoring baked into the narrative. Reddit's cleverest one-liners mixed into the synthesis where they fit, not dumped in a separate section.

skills/last30days/SKILL.md

@@ -330,12 +330,10 @@ Common patterns:
 - If digg-pp-cli is installed (check `which digg-pp-cli`): add Digg
 - If AUTH_TOKEN/CT0 or XAI_API_KEY or FROM_BROWSER is set, or xurl CLI is installed and authenticated: add X
 - If yt-dlp is installed (check `which yt-dlp`): add YouTube
-- If SCRAPECREATORS_API_KEY is set and INCLUDE_SOURCES contains tiktok: add TikTok
+- If SCRAPECREATORS_API_KEY is set: add TikTok, Instagram, Threads (suppress any of these via EXCLUDE_SOURCES)
-- If SCRAPECREATORS_API_KEY is set and INCLUDE_SOURCES contains instagram: add Instagram
+- If SCRAPECREATORS_API_KEY is set and the user explicitly requested pinterest for this query (e.g. via `--search=pinterest`): add Pinterest
-- If SCRAPECREATORS_API_KEY is set and INCLUDE_SOURCES contains threads: add Threads
-- If SCRAPECREATORS_API_KEY is set and INCLUDE_SOURCES contains pinterest: add Pinterest
 - If BSKY_HANDLE and BSKY_APP_PASSWORD are set: add Bluesky
-- If OPENROUTER_API_KEY is set: add Perplexity
+- If OPENROUTER_API_KEY is set and INCLUDE_SOURCES contains perplexity: add Perplexity
 - If EXCLUDE_SOURCES is set (comma-separated, case-insensitive): drop any matching source from the list above before displaying
 
 Then display (use "and more" if 5+ sources, otherwise list all with Oxford comma):

skills/last30days/scripts/lib/env.py

@@ -584,12 +584,12 @@ def _parse_include_sources(config: dict[str, Any]) -> set[str]:
 def is_threads_available(config: dict[str, Any]) -> bool:
     """Check if Threads source is available.
 
-    Requires SCRAPECREATORS_API_KEY AND 'threads' in INCLUDE_SOURCES.
+    Returns True when SCRAPECREATORS_API_KEY is set. Threads runs alongside
-    Threads is an opt-in source - it is not activated by default.
+    TikTok and Instagram as part of the SC family — same key, same per-call
+    cost shape, so the same default-on rule applies. Suppress via
+    EXCLUDE_SOURCES=threads.
     """
-    if not config.get('SCRAPECREATORS_API_KEY'):
+    return bool(config.get('SCRAPECREATORS_API_KEY'))
-        return False
-    return 'threads' in _parse_include_sources(config)
 
 
 def is_instagram_available(config: dict[str, Any]) -> bool:

tests/test_env_v3.py

@@ -42,5 +42,25 @@ class EnvV3Tests(unittest.TestCase):
                 self.assertIsNone(bird_x.is_bird_authenticated())
 
 
+class ThreadsAvailabilityTests(unittest.TestCase):
+    """Threads is in the SC default-on family: same key, same per-call cost
+    shape as TikTok / Instagram, so the same default-on rule applies.
+    Suppression goes through EXCLUDE_SOURCES, not gated opt-in."""
+
+    def test_threads_available_with_sc_key_only(self):
+        self.assertTrue(env.is_threads_available({"SCRAPECREATORS_API_KEY": "k"}))
+
+    def test_threads_unavailable_without_sc_key(self):
+        self.assertFalse(env.is_threads_available({}))
+        self.assertFalse(env.is_threads_available({"INCLUDE_SOURCES": "threads"}))
+
+    def test_threads_does_not_require_include_sources(self):
+        """Regression guard: INCLUDE_SOURCES should not be needed."""
+        self.assertTrue(env.is_threads_available({
+            "SCRAPECREATORS_API_KEY": "k",
+            "INCLUDE_SOURCES": "",
+        }))
+
+
 if __name__ == "__main__":
     unittest.main()