feat(prepass,explore): padding dies at the prompt; a refusal the model can act on is a return value [skip-docs]

Order 20260908T195801Z. Findings 4 and 5 from the S7 acid test, then the two things
finding 99 measured and deliberately did not fix (D3, D2).

No user-facing surface changes: no new flag, no new command, no changed output
contract. Both seams are internal (the pre-pass rendering, and the shape a tool
answers a model with), so [skip-docs] rather than a README edit that would describe
nothing an operator can do differently.

FINDING 4 -- MEASURED, NOTHING BUILT. K2's price schedule IS readable without
guessing (8 column spans, 71 of 91 non-blank rows give >= 2 cells, the split stable
for K = 2..64). But 0 of 92 rows name all three of code/quantity/unit_cost -- also
under a looser substring match -- and 0 of 91 data rows carry code + quantity +
amount. The triple is not formatted away; it is not in the document. It is a price
SUMMARY plus nine rate cards whose unit-price columns are empty (pre-award). The
order's binding decision rule therefore falls against building:
--derive-cost-baseline keeps refusing, and MAJOR-4's own honesty limit holds.

FINDING 5 -- BUILT. Measured on the actual rendering path (concept_text, not the
raw file): the delivered excerpt is 104 lines / 67 245 chars, carrying 208 interior
whitespace runs, 117 of them >= 100 and the longest 887 -- 56 806 of 67 245
characters = 84.5 %, over 72 of 104 lines. collapse_padding, called from
_data_blocks (the one renderer both arms share, and therefore AFTER
verify_against_bundle -- collapsing in concept_text would break every payload's own
digest), gives -72.4 %: line count invariant, non-whitespace byte-identical, leading
indentation untouched, no number changed.

F99-D3 -- read_file / read_dir / read_bundle now RETURN their refusal. MAF turns a
tool raise into "Error: Function failed." (_tools.py:1410-1432, :1427) and counts it
against DEFAULT_MAX_CONSECUTIVE_ERRORS_PER_REQUEST = 3, so everything the refusing
arm knows is destroyed on the way out. The gates are unchanged; the property they
exist for -- the reason travels, the bytes never do -- is now asserted explicitly on
the returned value. The arm is keyed on named classes, never bare Exception, because
ExplorationError is itself a RuntimeError subclass.

F99-D2 -- the invariant row, plus one for finding 5 (a stated deviation from "one
row only": finding 5 is a separately built seam and the ledger's standing rule
requires its own row).

19 existing arms rewritten, never deleted and never weakened: where the class
carried a distinction, the refusal KIND carries it now.

13 mutations, all red against the whole suite (W1-W5, M1-M8), each restored from
scratchpad with shasum -c. Control 1543 passed / 5 skipped (from 1529/5, a strict
superset, 0 removed). Golden demo-transcript.stdout unchanged
(shasum -a 1 of the CONTENT = ea8c534773acdbe41ae68f2c55724d69aaf8be4f).

Measurement: docs/2026-09-08-funn-4-5-og-read-nekt.md

Co-Authored-By: Claude <Opus 5>

tests/test_hierarchical_navigation_loadbearing.py

@@ -54,7 +54,6 @@ import json
 from pathlib import Path
 from typing import Any
 
-import pytest
 
 from portfolio_optimiser import explore, okf
 from portfolio_optimiser.explore import navigator_tools
@@ -269,11 +268,18 @@ def test_an_unknown_directory_is_refused_by_name(tmp_path: Path) -> None:
 
     Pinned to ``BundlePathNotFound`` by NAME since F3 added its sibling: both refusals quote the
     caller's path, so a match on the path alone could no longer tell "this is nothing" from "this
-    is a document" - the substring two branches share."""
+    is a document" - the substring two branches share.
+
+    REWRITTEN, not weakened (F99-D3): the tool RETURNS the refusal instead of raising it, so the
+    name it is pinned to is the ``refusal`` kind. Both halves stand - the path is quoted, and the
+    kind still separates it from ``DocumentPathRefused``."""
     base = _write_tree(tmp_path, "korpus", dirs=2, per_dir=2)
 
-    with pytest.raises(okf.BundlePathNotFound, match="kategori-99"):
-        _read_dir(base, "kategori-99")
+    refusal = _read_dir(base, "kategori-99")
+
+    assert refusal["refusal"] == okf.BundlePathNotFound.__name__
+    assert refusal["refusal"] != okf.DocumentPathRefused.__name__
+    assert "kategori-99" in refusal["refused"]
 
 
 # --- (h) the description must not lie about the body ----------------------------------------------