chore(v0.8.1): version bump + CHANGELOG + ARCHITECTURE.md for reaper

Bump plugin header and PRAUTOBLOGGER_VERSION 0.8.0 → 0.8.1. Patch
bump — the reaper is internal infrastructure; no user-visible UX
change.

CHANGELOG:
- Fixed: orphan `llm_research` rows now reaped daily.
- Added: WP-CLI `wp prautoblogger reap-research`; `_prautoblogger_run_id`
  post_meta is now written by Publisher on every post.

ARCHITECTURE.md:
- Decision #13 (Run-ID based log linking) cross-refs the new post_meta.
- New Decision #19 documents the reaper's scan/amortize/delete policy,
  the 1-hour grace window, the 7-day stale cutoff, and the one-shot
  activator back-populate migration.

DB schema unchanged — no PRAUTOBLOGGER_DB_VERSION bump.

Final commit of the v0.8.1 bundle.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ARCHITECTURE.md

@@ -521,7 +521,10 @@ The posts widget uses WordPress-bundled React (`wp.element`) with raw `createEle
 The widget fetches posts asynchronously from a dedicated REST endpoint rather than rendering server-side. This keeps initial page load fast and allows the endpoint to be cached independently (5-minute Cache-Control). The permission callback uses a filter (`prautoblogger_rest_posts_public`) so sites can restrict access if needed.
 
 ### #13: Run-ID based log linking
-Each pipeline execution generates a UUID (`run_id`) that tags every `prab_generation_log` entry. When a post is published, `link_generation_logs()` uses `UPDATE WHERE run_id = X` to associate entries with the `post_id`. This is more reliable than the previous timestamp-window approach, especially in batch runs where multiple posts are generated in quick succession.
+Each pipeline execution generates a UUID (`run_id`) that tags every `prab_generation_log` entry. When a post is published, `link_generation_logs()` uses `UPDATE WHERE run_id = X` to associate entries with the `post_id`. This is more reliable than the previous timestamp-window approach, especially in batch runs where multiple posts are generated in quick succession. **v0.8.1+**: `run_id` is also persisted on each post as `_prautoblogger_run_id` post_meta, giving the orphan-research reaper a direct path from run to siblings without walking the gen_log table (see #19).
+
+### #19: Daily orphan-research-row reaper (v0.8.1)
+When a pipeline dies between post creation and the final `Post_Assembler::amortize_research_costs()` call (Hostinger exec kill, OOM, LiteSpeed cut, fatal), the shared `llm_research` cost row stays in `prab_generation_log` with `post_id = NULL` and sibling articles understate their true cost in the breakdown popover. A new daily WP-Cron event `prautoblogger_reap_orphan_research_rows` (hooked to `PRAutoBlogger_Research_Reaper::on_cron`, 03:15 server time — 15 min after the primary generation cron) scans for orphan rows older than a 1-hour grace window, looks up sibling posts by `_prautoblogger_run_id` post_meta (fallback: distinct `post_id`s in gen_log for the same run_id), and delegates to the existing idempotent `amortize_research_costs()` on match. Orphans that still have no siblings after 7 days are deleted outright as sunk cost. A one-time activator migration (`prautoblogger_migrated_run_id_meta_v081`) back-populates `_prautoblogger_run_id` on existing posts from gen_log so the meta-primary path works on upgrade. Manual ops trigger: `wp prautoblogger reap-research`.
 
 ### #14: Reddit RSS replaces PullPush.io (and earlier Reddit OAuth)
 Reddit rejected our OAuth API application (April 2026). We initially switched to PullPush.io, but its index was frequently stale or unavailable. Reddit's RSS/Atom feeds (`/r/{sub}/hot.rss`) proved the most reliable option — they work from datacenter IPs where .json gets 403, require no auth, and have no apparent rate limit. The .json endpoints are kept as a fallback for posts and as the sole source for comment data. Each collected item's metadata includes a `data_source` field (`reddit_rss` or `reddit_json`) for auditability.