fix(search): show the passage that matched, not the opening of the body (#4243)

Raised by the operator: are we limiting what comes back by character count,
and how do we verify the pertinent part is the part displayed?

We were not. mcp/tools/search.py sent (note.body or "")[:240] — a head cut,
with no marker that anything had been removed, so a 240-character preview of
a 4000-character record was indistinguishable from a complete short one.

The opening is the wrong span. The match is semantic and per chunk, and
semantic_search_notes collapses to best-chunk-per-note — its own comment at
the collapse says "the first appearance of a note is its best chunk". So the
system identified the passage that earned the hit and then discarded it:
select(Note, distance) kept no chunk column. A record could rank first on its
sixth paragraph, be previewed by its first, and be judged irrelevant on a
span the search had already scored lower. That biases against long records,
and it is self-concealing — the caller who does not open it never learns the
preview was misleading.

  - embeddings: chunk_index/chunk_text ride along in the select, and the
    collapse records the winner in report["best_chunk"]. Carried in `report`,
    NOT by widening the return tuple: ten callers unpack (score, note) at
    ~18 sites and nothing would catch the misses (lesson #4207). `report` is
    the side-channel this function already uses for best_available_score.
  - search(): excerpt / excerpt_is / body_length, and read_full when there is
    more. A caller that cannot tell a matched passage from a document opening
    cannot judge whether to look deeper, which is the only decision the field
    supports.

elide() moves to services/text.py so both callers share one copy, and it
keeps BOTH ends with a stated gap — it is the fallback for when nothing
identifies a better span than "all of it", not the goal.

Also fixes a guard that produced a false failure on the previous commit:
test_pull_telemetry checked `"project_id: int = 0" in body.split("\n")[0]`,
which sees only the first line, so wrapping get_task's signature over four
lines made it report a function that does take the project as one that does
not. Parsed with ast now, and proven to still reject an absent or
wrongly-typed parameter rather than being appeased by reflowing the code.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

src/scribe/services/text.py

@@ -0,0 +1,38 @@
+"""Text shortening for surfaces that cannot show a record whole.
+
+One function, in one place, because both doors shorten and two copies would
+drift — and because the reasoning below is the part that matters and should
+not have to be re-derived at each call site.
+"""
+
+
+def elide(text: str, budget: int) -> tuple[str, bool]:
+    """Cut to `budget` characters from the MIDDLE, keeping both ends.
+
+    A head-only cut — `text[:800]` — decides what a reader sees by character
+    position, which is uncorrelated with what matters. Prose does not put its
+    conclusion first: a passage that opens with what was attempted and closes
+    with "so this shipped in 04775c3" loses exactly the sentence that answers
+    the question. Worse, the reader cannot tell: a truncation marker says that
+    something was removed, never whether it mattered, so the decision "should
+    I look deeper?" gets made on evidence selected by length.
+
+    So keep the opening (what this is about) AND the closing (where it landed),
+    and state in between how much went. Two thirds to the head because that is
+    where the subject is established; a conclusion needs less room to carry.
+
+    Returns (text, was_cut). A `budget` of 0 or less means no cut.
+
+    This is the fallback, not the goal. Where the system knows WHICH span of a
+    record is the relevant one — a semantic search knows exactly that, and
+    stores it (#4243) — show that span and say so. Reach for this only when
+    nothing identifies a better part than "all of it".
+    """
+    if budget <= 0 or len(text) <= budget:
+        return text, False
+    head_len = max(1, budget * 2 // 3)
+    tail_len = max(1, budget - head_len)
+    omitted = len(text) - head_len - tail_len
+    head = text[:head_len].rstrip()
+    tail = text[-tail_len:].lstrip()
+    return f"{head}\n\n[… {omitted} characters omitted …]\n\n{tail}", True