fix(lab): serving-boundary batch - drop the artificial drafting cap, honest errors, plane-true budget, conversion notes

Per Eli: no random/artificial caps. The 300k markdown cap was token policy
at the extraction layer; its throw was swallowed into a silent plaintext
whole-read fallback that cost MORE tokens than the markdown it refused
(antitrust market-data, ~84k tok). Removed - memory stays bounded by the
real package guards (input bytes, entry count, inflated XML bounds); token
exposure is a serving policy. The report now extracts (351k chars, 3.3s)
with an addressable 5.4k index.

Also: pandoc-missing ENOENT no longer misreported as malformed XML
(conversion failures keep naming the part); whole-read budget projects on
the plane actually served (markdown drafting surface when present, not
plaintext); MIKE_SERVE_CONVERSION_NOTES (OFF in all frozen arms) rides
extraction warnings on the FIRST read as a CONVERSION NOTES line at the
citation-reminder layer - coordinates and evidence segments untouched.

Proof: docx conformance 20/20; index+wiring suites 39/39; exposure probe
both flag states; notes probe both flag states on the real warnings doc.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011pfUVhNFTRvhYGXBwoKNj6