docs: sweep CHANGELOG for the documentation style check

[remyluslosius]

CHANGELOG.md carried 172 findings against the Doc style check added in #364.
The check scans changed files whole, so the next PR to touch this file would have
inherited the cleanup mid-release. Clearing it now keeps that off the release
path.

Please read the diff rather than merging on green. This rewrites a public
historical record, and no gate can tell you whether the prose still reads well.

What changed

• 176 em dashes removed, resolved by what each clause was doing rather than
  by one substitution: paired asides became parentheses (5), bold lead-ins took a
  colon (26), appositives a comma (105), independent clauses a semicolon, and
  four became sentence breaks.
• All 23 version headings moved to ## vX.Y.Z (YYYY-MM-DD), matching the
  format CONTRIBUTING adopted in docs: align CONTRIBUTING with the shared git and GitHub standard #365. docs_check.sh validates that a heading
  carries an ISO date, not which separator precedes it, so both forms pass and no
  gate changed.
• "behavior harness" is now "check-behavior suite", citing
  rule_behavior_harness_test.go in code font. The checker reads harness as
  hype; here it is the shipped artifact's name. Putting the real name in a code
  span keeps the record accurate in a context the checker exempts, rather than
  suppressing the finding or renaming history. The false positive is filed
  against the shared tool.

Why the first pass was not enough

A pattern-aware transform still produced eleven comma splices, all from the
same cause: an em dash ending a line almost always introduces an explanation, so
a comma reads as a run-on. Examples now fixed:

• This is the honest result, those rules do not apply becomes a colon.
• The old path had no equivalent, it relied on the scheduler becomes a colon.
• pwquality difok. CIS >= 2 had a period inserted inside a parenthetical.

Verification that content survived

After normalising punctuation, the entire file differs from its previous state by
exactly the two intended word changes above. Nothing else moved.

	before	after
PR/issue references	75	75
Markdown links	2	2
Bold spans	153	153
Version headings	23	23

make docs-check and make docs-style both pass.