feat(retrieval): the wide net becomes a pull — fifty candidates, no bar (#4103)

Milestone 416 step 5. The operator's compromise — "if you're worried
about excluding potentially important data let limit it to 50 entries"
— moved to the surface where it is safe. Fifty in the push would be
milestone 394 with extra steps; fifty in a pull crowds nothing out.

`what_might_apply(query)` returns ranked rule candidates with NO
threshold. The moment it serves is the one where the caller does not
trust a bar to decide for them, so it does not have one — every row
carries its score and the reader judges.

WHY IT IS NOT A BIGGER `limit` ON `search`

`_search_rules` returns statement, why and how_to_apply in full, on the
stated reasoning that a caller who went looking deserves the whole
record. That is the DEEP pull and should stay that way. This is the
SHALLOW one — many candidates, each just enough to decide whether to
open it. Opposite trade-offs, so it is a second tool.

THE PREMISE THE STEP GOT WRONG

The task said fifty "costs nothing". `_rule_hint_line` had already
measured otherwise: ~143 tokens per line once the trigger is rendered,
and #3855 tripled trigger lengths across the corpus. Fifty is ~7,000
tokens — cheap next to an arm firing before every Bash call, but not
free, and a tool promising a free wide net gets reached for casually
and then regretted.

So it reuses the graduated shape #3851 measured for the push: the top
few carry their trigger whole, the rest carry a cut of it. TRUNCATED,
never dropped — the trigger is what lets a reader judge without
opening, and a teaser without one is just an id. The cut borrows
`_goal_line`'s technique including the fallback that matters (#4036):
`textwrap.shorten` returns a bare "…" for one unbroken word.

TELEMETRY

Logged under its own pull source, asserted absent from both the tunable
push registry and AMBIENT_SOURCES. That guard is load-bearing right
now: the push arms' near-miss distributions are the evidence #4121
argues from, and a pull folded into them would move those numbers.

INSTRUCTION SURFACES

The using-scribe reflex and the MCP instructions both pointed at
`search(content_type="rule")` for the consequential moment — the deep
tool, at the moment you want breadth. They now point here, and keep
`search` for reading a rule you already suspect. Written as a practice
rather than a prohibition (rule 165).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01821k5B3Ysecp9fNYs92Kuy

plugin/skills/using-scribe/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: using-scribe
-description: Use at the START of every session, and before answering anything about the operator's work or starting any task — establishes the Scribe-first reflex. You hold none of the operator's rules: they arrive by retrieval when your work matches one, and search(content_type="rule") is how you ask before a consequential act. Call enter_project when a repo/project is in scope. Then recall before acting, update over duplicate, plan in Scribe not in files.
+description: Use at the START of every session, and before answering anything about the operator's work or starting any task — establishes the Scribe-first reflex. You hold none of the operator's rules: they arrive by retrieval when your work matches one, and what_might_apply is how you ask before a consequential act — it returns the wide net of candidates with no bar. Call enter_project when a repo/project is in scope. Then recall before acting, update over duplicate, plan in Scribe not in files.
 ---
 
 # Using Scribe
@@ -73,9 +73,19 @@ Two constraints on *how* that's achieved:
 
    So "no rule arrived" means "nothing matched", never "no rule exists" — an
    empty session is not evidence of an empty rulebook. Retrieval fires when
-   something asks: before a consequential act, `search(content_type="rule")` on
-   what you are about to do, and pull a record's full statement with
-   `get_rule(id)` when it is about to bite. When a project is in scope, pass
+   something asks, so ask — and reach for the tool that fits the moment:
+
+   - **Before a consequential act**, and before handing work back because you
+     are unsure you may finish it: `what_might_apply("what you are about to
+     do")`. It returns up to fifty ranked candidates with NO bar. The arms that
+     push rules at you spend a budget of three and say nothing about what sat
+     just underneath — right for something firing before every command, wrong
+     for the one moment you actually want to be sure. Expect the tail to be
+     noise; you are reading for the one record you would have missed.
+   - **When you already suspect a particular rule**: `search(content_type=
+     "rule")` for full statements, or `get_rule(id)` when it is about to bite.
+
+   When a project is in scope, pass
    its `project_id`: the answer is then the global rules plus that project's
    own, never another project's. `enter_project(id)` lists the project's own
    rules by title.