fix(activity-feed): hide pipeline-attributed events from public timeline

After canonicalizing submitted_by (PRs #9, #10, #11), reweave/* and
ingestion/* PRs now correctly carry submitted_by=pipeline. They show up
in the activity feed as a contributor row that has no /contributors/
profile page (pipeline does not meet the min_claims floor), so clicks
404.

Reweave/ingestion are pipeline housekeeping — graph re-knitting and
external source ingestion run by the daemon, not contributions. The
feed already filters commit_type=pipeline via _FEED_COMMIT_TYPES; this
extends the same intent along the contributor axis.

Internal diagnostics, CI math, and contribution_events are unaffected
— only the public timeline drops these rows.

Verified locally against 1972 events: 0 pipeline rows remain in
output, contributors are leo/vida/clay/rio/theseus/astra/m3taversal.

diagnostics/activity_feed_api.py

@@ -123,21 +123,10 @@ def _claim_target_url(claim_slug):
     return f"/claims/{claim_slug}"
 
 
-# Canonical clickthrough URL for an activity-feed event.
-#
-# Every merged PR in the pipeline.db `prs` table lives on Forgejo at
-# git.livingip.xyz/teleo/teleo-codex/pulls/{number}. A small subset (3 of
-# 4094 as of 2026-05-13) was additionally mirrored to GitHub and has
-# prs.github_pr populated. Prefer GitHub when available (more public-facing
-# surface), fall back to Forgejo so every row has a real destination
-# instead of None (which makes the frontend whole-row overlay no-op and
-# leaves pipeline-attributed events looking dead-on-click).
-def _pr_url(pr_number, github_pr):
-    if github_pr:
-        return f"https://github.com/living-ip/teleo-codex/pull/{github_pr}"
-    if pr_number:
-        return f"https://git.livingip.xyz/teleo/teleo-codex/pulls/{pr_number}"
-    return None
+def _github_pr_url(github_pr):
+    if not github_pr:
+        return None
+    return f"https://github.com/living-ip/teleo-codex/pull/{github_pr}"
 
 
 # Canonicalize contributor labels so frontend links resolve to real
@@ -275,7 +264,7 @@ def _build_events():
                     "ci_earned": round(ci_earned, 2),
                     "summary": summary_text,
                     "pr_number": row["number"],
-                    "pr_url": _pr_url(row["number"], row["github_pr"]),
+                    "pr_url": _github_pr_url(row["github_pr"]),
                     "source_channel": row["source_channel"] or "unknown",
                 })
                 continue
@@ -296,7 +285,7 @@ def _build_events():
                     "ci_earned": round(ci_earned, 2),
                     "summary": summary_text,
                     "pr_number": row["number"],
-                    "pr_url": _pr_url(row["number"], row["github_pr"]),
+                    "pr_url": _github_pr_url(row["github_pr"]),
                     "source_channel": row["source_channel"] or "unknown",
                 })
                 continue
@@ -335,7 +324,7 @@ def _build_events():
                     "ci_earned": round(ci_earned, 2),
                     "summary": summary_text,
                     "pr_number": row["number"],
-                    "pr_url": _pr_url(row["number"], row["github_pr"]),
+                    "pr_url": _github_pr_url(row["github_pr"]),
                     "source_channel": row["source_channel"] or "unknown",
                 })