refactor(mcp): _INSTRUCTIONS orients the workflow, not a rulebook (#4389)

Spike #4389 read the spec, Claude's docs and a dozen servers: the field is
for how the tools fit together, and the field runs ~600-1,600 characters.
Ours sat at the 2,048 cap as a keyword index that also carried stance.

- JUDGE, REPORT and MISSED leave the index. They fire mid-work, not at
  session start; using-scribe and reporting-back state them in full, and
  `placement`/`report_back` cue reporting in-band. No skill text changes.
- The rest is rewritten as plain practices (1,503 chars) and keeps every
  session-start marker the ownership registry pins.
- INSTRUCTIONS_BUDGET 2000 -> 1600; the three index markers are dropped
  from the registry; the miss-route index test now checks that the index
  keeps what_might_apply and stays off the route.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/scribe/mcp/server.py

@@ -23,49 +23,48 @@ from quart import Quart
 #     client's own conventions, never a copy of the above.
 # tests/test_guidance_ownership.py holds the topic registry that enforces it.
 #
-# THIS BLOCK IS THE SERVER'S ORIENTATION, WRITTEN AS AN INDEX. It reaches
-# every MCP client, so it names no client, and it points at where each reflex
-# is stated rather than restating it. A new topic gets a line here only if it
-# is a session-start reflex; its full statement goes to its owner.
+# THIS BLOCK IS THE SERVER'S ORIENTATION: the workflow across tools. It reaches
+# every MCP client, so it names no client, and it points at where each practice
+# is stated rather than restating it. What belongs here, per the spec and the
+# field (spike #4389): how the tools fit together — which to call first, which
+# before which. What does not: a tool's own contract (its description carries
+# it), and stance — who judges, how to report, what a missed rule means. Those
+# fire mid-work, not at the start; the skills state them and in-band responses
+# (`placement`, `report_back`) cue them at the moment they apply. A new topic
+# gets a line here only if it is a session-start practice.
 #
-# BUDGET: at most 2,000 characters (test_instructions_fit_the_fold). Claude
+# BUDGET: at most 1,600 characters (test_instructions_fit_the_fold). Claude
 # Code injects only the first ~2,048 characters of a server's instructions and
 # cuts the rest mid-word (#2562, observed live), and other clients differ, so
-# nothing load-bearing may sit past the fold. The history of what was traded
+# nothing load-bearing may sit past the fold; the rest of the field runs
+# ~600–1,600 (#4389), and a block pressed against the cap is being used as a
+# rulebook. The history of what was traded
 # for space before the ownership split (milestones 317, 333, 409) is in
 # decision #4027 and the notes it supersedes.
 _INSTRUCTIONS = """
 Scribe is the operator's system of record, and yours: recall before acting,
-record as you go, keep one copy here rather than in local memory files.
+record as you go, keep one copy here rather than in local memory files. Each
+practice below is stated in full in the using-scribe skill (if your client
+reads Agent Skills) and in each tool's description.
 
-Each reflex is stated in full in the using-scribe skill (if your client reads
-Agent Skills) and each tool's description. The index:
-- ORIENT: enter_project(id) loads the project, open work, Systems and design
+- Start with enter_project(id): the project, open work, Systems and design
   system. An `inception` key: ask what it inherits, then
   decide_project_inception.
-- RULES: nothing preloads; a rule arrives when your work matches it. Before a
-  consequential act, what_might_apply("what you are about to do") — fifty
-  ranked, no bar. search(content_type="rule") reads one you suspect. Silence
-  means nothing matched, not none. Rules bind; preferences guide and you keep
-  them current; lessons inform.
-- MISSED: a rule that missed you is a trigger to fix, not a floor to move
-  (retrieval_telemetry).
-- JUDGE: you are the judge of record — what a shape is, whether a finding
-  holds, whether work is done. Surfacing one for them to rule on is the
-  judgment not made. Escalate their acts, not your decisions.
-- RECALL: search before acting, scoped with the active project_id.
-- RECORD: create_task; a fix is kind="issue". add_task_log as you go; status
-  in_progress on start, done on finish. Tag system_ids.
-- PLAN with an arc: find the existing plan first
-  (search(content_type="milestone")) and add steps to it; else
-  start_planning(steps=[...]).
-- IDS exist only once a create returns them. Records citing each other go
-  through create_records, writing {{ref:N}} for the Nth record.
-- REUSE: search snippets before building; create_snippet what you build.
-- UI: the project's design system binds; resolve_design_system before
+- Rules are not preloaded; one arrives when your work matches it. Before a
+  consequential act, what_might_apply("what you are about to do");
+  search(content_type="rule") reads one you suspect. Silence means nothing
+  matched, not none. Rules bind; preferences guide and you keep them current;
+  lessons inform.
+- Search before acting or building, scoped with the active project_id; start
+  from a recorded snippet, and create_snippet what you build.
+- Work is tasks (a fix is kind="issue"): in_progress on start, add_task_log as
+  you go, done on finish; tag system_ids.
+- A plan is a milestone: find the existing one
+  (search(content_type="milestone")) before start_planning.
+- IDs exist only once a create returns them; records citing each other go
+  through create_records, writing {{ref:N}} for the Nth.
+- In UI work the project's design system binds: resolve_design_system before
   hand-writing a value.
-- REPORT from the `placement` a task write returns: where it sits, what
-  changed, what needs them, what next.
 
 Creates are duplicate-gated: a near-match returns the existing id to update.
 shared:true records are another user's suggestion, not settled practice.