fix(code/edit): forgive flat/bare-string edit_mode + reject placeholder paths — the two barriers past the search-loop

[joelteply]

Glass-boxed live (loop-perception PR #1950 got the 14B PAST the search-loop and hammering code/edit; these are the
two walls it then hit):

1. edit_mode shape: it sent edit_mode:"append" (bare variant string) and, later, the fields flat at top level with
   no edit_mode at all. EditMode is a serde-tagged enum, so both 400'd at deserialize. Fix: edit_mode accepts a
   Value; normalize_edit_mode tries the strict tagged object first (unchanged), then a bare mode string, then
   INFERS the mode from which top-level fields are present (search/replace→search_replace, content→append, etc.),
   failing LOUD and naming the missing field (never a silent no-op → false-zero). Same "meet the model halfway"
   forgiveness as code/search fix(code/search): forgive glob-shaped pattern — list files instead of looping the search forever #1949; strict callers are untouched, so no regression.

2. placeholder path: it wrote file_path:"<path_to_blueprints.py>" — echoing the schema's angle-bracket placeholder
   instead of the concrete path it had already seen in its search results. reject_placeholder_path fails loud on
   <...>/path_to/your_file templates and points at the real value ("use the path from your search results, e.g.
   src/flask/blueprints.py") instead of a confusing file-not-found.

VALIDATED live: with these, the inference path fires (she now sends content/search flat and the mode resolves) — the
remaining 0-diff is purely the placeholder path, which now fails loud with guidance instead of silently. Unit-tested
(strict/bare/inferred/loud-missing; placeholder-vs-real). The rails are now maximally forgiving; what's left past
this is base-model COHERENCE (it has the real path in memory but writes the template) — the Devstral lever, not more
tool fixes. [[px-persona-experience-tools-as-good-ux]] [[built-to-teach-lesser-tuned-intelligences-win]]

Co-Authored-By: Claude Opus 4.8 noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_01LoTjvf5j3Ez13g6k8mRkFo