feat(layout): measure compiled PDF layout instead of eyeballing it (#378)

* feat(layout): measure compiled PDF layout instead of eyeballing it

/apply Step 5b asks for layout properties and executes none of them: they are
checked by reading the rendered page, which is exactly how they get missed.

The failure that motivates this is silent under every existing check. A moderncv
\cventry renders as a tabular, so an entry is one unbreakable block; when it does
not fit in the space left, the whole entry moves to the next page and leaves a
hole behind. The document still compiles, still reports the expected page count,
and still passes tools/verify_pdf.py. Observed in the wild at 273pt, roughly 19
blank lines, mid-page, on a CV whose visual read looked fine.

tools/verify_layout.py reports per page where the text starts and stops, bottom
whitespace as a share of page height, and the largest gap between lines, then
exits 1 on a hole over 100pt, a non-final page ending more than 25% early, body
text colliding with the page-number footer, a final page more than 35% empty, or
an entry header or section heading stranded at a page break.

Page count is deliberately not checked here - verify_pdf.py --pages already does
that, and two implementations of one rule drift. Geometry comes from Poppler
pdftotext -bbox, already a dependency; a missing Poppler exits 2 with "skipped:"
rather than failing the run.

Tests build synthetic Page/Line geometry, so the suite needs neither Poppler nor
a LaTeX toolchain and runs on the existing 3.10-3.14 matrix.

* fix(layout): survive Windows encoding and a pdftotext without -bbox

Review found two failures on the repo's primary platform:

subprocess.run(..., text=True) decoded pdftotext's UTF-8 output with the
Windows ANSI codepage and crashed on the stock cv/main_example.pdf. It now
passes encoding="utf-8" with errors="replace" at the call site, matching the
fix verify_pdf.py already carries from #369.

Git for Windows ships an xpdf-based pdftotext that shadows Poppler in a
default PATH and has no -bbox flag; it exited 99, the CalledProcessError
escaped, and the run ended in exit 1 - indistinguishable from a real layout
problem, which would send /apply chasing a phantom hole. That now routes to
the existing "skipped:" exit 2 path with a message naming the likely cause,
covered by three tests on the extractor-failure path.

Also from review:

- .claude/settings.json and security_guards.py gain the verify_layout.py
  permission entries. apply.md Step 5b runs the tool on every /apply, so
  without them every run prompts.
- The docstring and CHANGELOG no longer call Poppler a dependency
  verify_pdf.py relies on. Since #369 verify_pdf prefers pypdf and Poppler is
  the fallback; word bboxes have no pypdf equivalent, so this is the one step
  that still wants it, and that is now what the text says.
- Docstring and apply.md state that the thresholds are calibrated for the
  stock moderncv and cover.cls geometry, and that the shipped example CV
  fails the thin-final-page rule by design.
- largest_gap documents that it measures top-to-top, so a tall line inflates
  the gap by its own height - over-detection, the safe direction.
- The test module imports via tools.verify_layout like test_verify_pdf.py
  instead of sys.path.insert.

* fix(verify_layout): quote only the first stderr line in the skip message (#378)

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013fqqLgQSnwgWkv98twQhHi

---------

Co-authored-by: Mads Lorentzen <madslorentzen_17@hotmail.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

CHANGELOG.md

@@ -28,6 +28,23 @@ per-file diff commands.
   resolves confirmed rows to `no_response`, logs dated entries to `notes`, updates archive
   `outcome.md` files, and hands off to calibration when 3+ applications are resolved.
 
+- **Mechanical layout verification for compiled PDFs** - `tools/verify_layout.py` measures
+  what `/apply` Step 5b previously only eyeballed: per-page text extent, bottom whitespace,
+  the largest internal vertical gap, footer collisions, and entry headers or section
+  headings stranded at a page break. It exists for a failure that survives every existing
+  check - a moderncv `\cventry` is an unbreakable `tabular`, so an entry that does not fit
+  jumps to the next page and leaves a hole behind (observed at 273pt, roughly 19 blank
+  lines) while the document still compiles, still reports the correct page count, and still
+  passes `tools/verify_pdf.py`. Geometry comes from Poppler `pdftotext -bbox`; Poppler is
+  optional repo-wide (since #369 `verify_pdf.py` prefers pypdf), and word bounding boxes
+  have no pypdf equivalent, so this is the one step that still wants it. A missing Poppler
+  - or the xpdf-based `pdftotext` Git for Windows puts ahead of it in PATH, which rejects
+  `-bbox` - degrades to a `skipped:` exit 2 rather than reporting a phantom layout failure.
+  Page count is deliberately left to `verify_pdf.py --pages` so that one rule keeps one
+  implementation. Thresholds are calibrated for the stock moderncv and `cover.cls`
+  geometry. Tests use synthetic page geometry, so they need neither Poppler nor a
+  LaTeX toolchain.
+
 ### Fixed
 
 - **`jobnet-search detail` no longer reports an externally hosted ad as not found** (#432) -