fix(review): correct diff-compression line numbers, prior-review dedupe, triage skip

Four defects, all found reviewing PR #9 (two of them by pragent-bot's own
review of that PR, which the anchoring bug then misplaced):

* compress_diff dropped context lines but copied the original `@@` hunk
  header verbatim, so the header no longer described the lines beneath it.
  parse_diff_anchors then walked stale headers and produced anchor sets
  shifted by the number of elided lines, misplacing inline comments or
  demoting them to bullets. Each surviving run of lines is now re-emitted as
  its own hunk with a recomputed `@@ -a,b +c,d @@`, so the output stays a
  valid unified diff whose numbers describe the real post-change file. The
  pseudo-marker `@@ … N context line(s) omitted … @@` is gone; it parsed as
  a hunk header and reset the anchor counter to 0. Anchoring additionally
  runs on the raw diff now, so the prompt window can never shrink the
  anchorable set.

* compress_diff's `_FILE_HEADER` regex matched diff *body* lines: a removed
  YAML `---` separator or an added `++` line was read as a file header,
  truncating the hunk and dropping its `@@` header with it. Body detection
  is now prefix-based, with a full-shape hunk-header regex.

* extract_finding_bullets could not match the bullets pragent itself posts:
  summary_bullets renders an emoji severity badge between the `-` and the
  `[SEV]` tag, which the regex rejected, so compact_prior_reviews always
  returned [] and every re-review repeated its previous findings.

* triage returning `{"lenses":[]}` — documented in .opencode/agents/triage.md
  as "no lens has surface, skip the fan-out" — ran every lens instead, since
  _intersect_with_triage mapped an empty selection to "all" and the call site
  had a second `or reviewers` fallback. `[]` and None are now distinct
  outcomes: `[]` skips, None fails open. A roster naming only unknown lens
  ids now fails open rather than silencing the review. The skip path returns
  a well-formed empty-findings response instead of "", which had landed in
  ai_review's unparseable-output branch and posted "AI review produced no
  parseable output" — a malfunction message for a normal verdict.

Also: non-URL references (a CVE id, a doc title) rendered as
`[CVE-2024-1234](CVE-2024-1234)`, a broken relative link in Gitea — now
plain text. PRAGENT_DIFF_CONTEXT and friends parse through _int_env, so a
typo logs and falls back instead of killing a review mid-flight. Removed
format_usage_section, dead since the collapsible usage block replaced it and
carrying a duplicate copy of the price-target logic.

Tests: 290 -> 301. New coverage for hunk-header fidelity before/after
compression, header-shaped content lines, the bullet round-trip against the
real renderer, and triage's three outcomes (previously untested).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B11e8TZZxJyzHW7jj7KWUN

tests/pilot/test_diff_compress.py

@@ -1,5 +1,6 @@
 """Unit tests for pragent pilot diff_compress. No network."""
 import os
+import re
 import sys
 
 HERE = os.path.dirname(os.path.abspath(__file__))
@@ -20,7 +21,7 @@ diff --git a/src/a.py b/src/a.py
 index 1..2 100644
 --- a/src/a.py
 +++ b/src/a.py
-@@ -1,10 +1,11 @@
+@@ -1,20 +1,21 @@
  ctx1
 -removed
 +added
@@ -30,8 +31,17 @@ index 1..2 100644
  ctx5
  ctx6
  ctx7
-+extra
  ctx8
+ ctx9
+ ctx10
+ ctx11
+ ctx12
+ ctx13
+ ctx14
+ ctx15
+ ctx16
++extra
+ ctx17
 @@ -20,3 +21,4 @@
  tail1
  tail2
@@ -76,11 +86,12 @@ def test_compress_diff_negative_disables_compression():
     assert orig == kept
 
 
-def test_compress_diff_collapsed_gap_marker():
-    # Two +/- lines separated by 14 context lines, context=2 — the gap between
-    # them is 10 dropped lines (between the +/- windows), which exceeds the
-    # 5-line marker threshold. The marker tells the reviewer there's more code
-    # between the kept hunks.
+def test_compress_diff_collapsed_gap_splits_into_two_hunks():
+    # Two +/- lines separated by 14 context lines, context=2. The dropped
+    # middle is expressed by SPLITTING the hunk in two, each with a recomputed
+    # `@@` header — not by a pseudo-marker line. `parse_diff_anchors` reads
+    # `@@` headers to reset its line counter, so anything that looks like a
+    # header but isn't one silently misanchors every following comment.
     middle = "\n".join(f" m{i}" for i in range(14)) + "\n"  # trailing \n!
     diff = (
         "diff --git a/x.py b/x.py\n"
@@ -95,7 +106,12 @@ def test_compress_diff_collapsed_gap_marker():
     )
     text, _, _ = compress_diff(diff, context=2)
     assert "+a" in text and "+b" in text
-    assert "@@ …" in text and "context line(s) omitted" in text
+    for m in ("m2", "m3", "m4", "m5", "m6", "m7", "m8", "m9", "m10", "m11"):
+        assert f" {m}\n" not in text  # the gap itself is gone
+    # Two hunks, and every emitted header is a real unified-diff header.
+    headers = [ln for ln in text.splitlines() if ln.startswith("@@")]
+    assert len(headers) == 2
+    assert all(re.match(r"^@@ -\d+,\d+ \+\d+,\d+ @@", h) for h in headers)
 
 
 def test_compress_diff_strips_no_newline_marker():
@@ -245,4 +261,78 @@ def test_compress_diff_preserves_anchors_for_post_change_lines():
     anchors = ai_review.parse_diff_anchors(text)
     assert 12 in anchors["x.py"]  # +new
     # ctx_a is within 1 line of +new at line 12, so kept.
-    assert 11 in anchors["x.py"]
+    assert 11 in anchors["x.py"]
+
+def test_compress_diff_keeps_post_change_line_numbers_exact():
+    # The regression that motivated the hunk-header rewrite: dropping context
+    # lines without renumbering shifted every anchor. Here `+new` really is
+    # line 10 of the post-change file; compression must not move it.
+    raw = (
+        "diff --git a/x.py b/x.py\n"
+        "--- a/x.py\n"
+        "+++ b/x.py\n"
+        "@@ -1,12 +1,12 @@\n"
+        + "".join(f" l{i}\n" for i in range(1, 10))
+        + "-old\n"
+        + "+new\n"
+        + " l11\n"
+    )
+    import ai_review
+    raw_anchors = ai_review.parse_diff_anchors(raw)["x.py"]
+    assert 10 in raw_anchors  # +new
+    text, _, _ = compress_diff(raw, context=1)
+    comp_anchors = ai_review.parse_diff_anchors(text)["x.py"]
+    # Compression only ever drops anchors; it never invents or moves one.
+    assert comp_anchors <= raw_anchors
+    assert 10 in comp_anchors  # +new still anchors to its real line
+
+
+def test_compress_diff_content_line_starting_with_dashes_is_not_a_header():
+    # A removed YAML document separator renders as `----`; an added one as
+    # `+++new`. Treating those as file headers truncated the hunk body and
+    # dropped the `@@` header with it.
+    diff = (
+        "diff --git a/x.yml b/x.yml\n"
+        "--- a/x.yml\n"
+        "+++ b/x.yml\n"
+        "@@ -1,4 +1,4 @@\n"
+        " a: 1\n"
+        " b: 2\n"
+        "----\n"
+        "+++new\n"
+        " c: 3\n"
+    )
+    text, _, _ = compress_diff(diff, context=1)
+    assert "----" in text and "+++new" in text
+    # The hunk header survives, so the body is still anchorable.
+    headers = [ln for ln in text.splitlines() if _is_hunk_header(ln)]
+    assert len(headers) == 1
+    import ai_review
+    assert ai_review.parse_diff_anchors(text)["x.yml"] == {2, 3, 4}
+
+
+def _is_hunk_header(line: str) -> bool:
+    return bool(re.match(r"^@@ -\d+,\d+ \+\d+,\d+ @@", line))
+
+
+def test_extract_finding_bullets_matches_current_renderer_output():
+    # The prior-review dedupe is only worth anything if it can read the
+    # bullets pragent itself posts. `summary_bullets` renders an emoji badge
+    # between the `-` and the `[SEV]` tag, which the original regex rejected.
+    import ai_review
+    findings = [
+        {"path": "a.py", "line": 10, "severity": "high",
+         "problem": "boom", "fix": "guard it", "suggestion": "", "reference": ""},
+        {"path": "b.go", "line": 0, "severity": "low",
+         "problem": "nit", "fix": "", "suggestion": "", "reference": ""},
+    ]
+    body = ai_review.format_review_body(
+        ai_review.summary_bullets(findings), "m", "abc123",
+        findings_for_table=findings,
+    )
+    bullets = extract_finding_bullets(body)
+    assert len(bullets) == 2
+    assert any("a.py:10" in b and "boom" in b for b in bullets)
+    # `**Fix:**` continuation lines are prose, not findings.
+    assert all("**Fix:**" not in b for b in bullets)
+    assert ai_review.compact_prior_reviews([body]) != []