BIP93: Refactor format and seed sections #2285

Group the regular and long checksum definitions in the codex32 format
section. Move the master-seed application profile to the end of the
specification and keep seed-specific checksum motivation in the
rationale.

This is a behavior-neutral organization change on top of the #2258
profile commit.

Keep the common format rules and checksum properties in one place, and replace the broad application-validity sentence with a concrete reference to the master seed requirements.

Remove the redundant symbol encoder and decoder examples. Preserve their validation rules in the format and master seed text, including the encoded-length restriction for both secrets and shares. Retained checksum and interpolation code is unchanged.

Checked retained Python ASTs against eb7bb6c, all 36 valid and 55 invalid vector occurrences, all six size mappings, legacy sizes, 1024 header combinations, checksum boundaries, share recovery, and nonzero padding. Link-format, README table, and whitespace checks pass.

Refs: #2258, #2285

Let readers implement unshared master seeds from the format and master
seed sections without reading the secret sharing procedures. Keep the
common header and unshared-secret rules under codex32, and group share
generation and recovery under SSSS-awareness.

Give checksum and error correction one TOC entry each. Use bold labels
for the individual checksums and generation cases, and preserve both
MediaWiki anchors and GitHub permalinks for demoted headings. Put the
interpolation helpers with generation and its recovery wrapper afterward.
Retained executable code is unchanged.

Checked the retained Python ASTs, existing valid/invalid vectors, size
mappings, header combinations, checksum boundaries, recovery, and padding.
Inspected the rendered TOC and table and checked fragment targets.
Link-format, README table, and whitespace checks pass.

Refs: #2285

Describe seed sizes in bits in the encoding instructions, checksum
rationale, and retained-size list, matching generation and the vectors.
Keep bytes for decoded output and the historical contiguous byte-size
range, and retain both units in the size table.

The supported sizes and all numeric constraints are unchanged. The
existing rationale already explains that BIP39 produces 512-bit seeds.

Checked retained Python ASTs, all existing vector occurrences, size
mappings, header combinations, checksum boundaries, recovery, padding,
and rendered markup. Link-format, README table, and whitespace checks
pass.

Refs: #2258, #2285

Add a reverse-chronological draft changelog and matching Version header
so readers can distinguish the earlier checksum-boundary and seed-size
changes from this behavior-neutral reorganization.

Assign retrospective versions to significant revisions and use their
upstream integration dates, rather than individual patch author dates.
Keep the Draft status and BSD-3-Clause license unchanged.

Checked the historical entries against first-parent upstream history,
the version and date ordering, and the metadata-only diff. Python ASTs,
existing vectors, size and checksum boundaries, header combinations,
recovery, padding, rendered markup, link formatting, README table, and
whitespace checks pass.

Refs: #2258, #2285

Define the integer-list representation once in the SSSS-awareness
introduction, before either procedure needs it. Move the unchanged
interpolation helpers there too, so recovery does not depend on code
inside Generating shares. Describe interpolation's arguments and result
beside its definition and refer to the shared representation from both
generation and recovery.

State that both checksum variants use the same procedures without an
early reference to the interpolation function. Label the existing casing
rules and remove the unnecessary word "workflows" from the rationale.
No algorithms, validity conditions, version, or changelog entries change.

Checked all Python blocks are byte-identical and that vectors, procedure
conditions, casing rules, headings, anchors, and metadata are unchanged.
Sixteen recovery cases pass using only the shared introduction and
recovery snippets, covering regular and long checksums. Existing vector,
size, header, checksum-boundary, recovery, and padding checks also pass.
Local rendering, link formatting, README table, and whitespace checks
pass; the casing label does not add a TOC entry.

Refs: #2285