perf(runtime-tags): let a conditional bound its own section

[DylanPiercey]

A section whose only content is an <if> chain was still emitting boundary markers and an anchor to delimit a range the conditional's own branch already bounds — three comment nodes per item for a <for> over a conditional. The section now emits none of them, and the rendered branch is the section's range; on each swap the conditional retargets any owner still holding the replaced range. When the chain renders nothing its anchor bounds the section instead, so this covers a chain with no <else> as well.

Worth ~12% on rebuilding a large keyed list, and removes every comment marker the conditional produced (42 to 0 in a chat-style fixture, matching a markerless framework's node count exactly). Costs +84 bytes brotli.

[changeset-bot]

🦋 Changeset detected

Latest commit: 4f6aeaa

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@marko/runtime-tags	Patch

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[codecov]

Codecov Report

❌ Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.35%. Comparing base (3ba2287) to head (4f6aeaa).

Files with missing lines	Patch %	Lines
packages/runtime-tags/src/dom/control-flow.ts	93.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3711      +/-   ##
==========================================
+ Coverage   90.34%   90.35%   +0.01%     
==========================================
  Files         414      414              
  Lines       19746    19767      +21     
  Branches     3615     3626      +11     
==========================================
+ Hits        17840    17861      +21     
  Misses       1367     1367              
  Partials      539      539              

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[DylanPiercey]

Superseded by #3712, which gates the same two getSectionMeta lines on a strictly weaker condition (any if/for/dynamic tag at a section edge, rather than an exhaustive conditional as the whole content), so every shape this elides is elided there too — verified by compiling this PR's own target shape on both branches. #3712 also drops the leftover leading over(1) walk step this leaves behind, and extends the same owner-retargeting walk to <for>, <show>/<await>/<try>, lazy tags and the resume path.