fix(snippets): bind the action slot on the 4.5 LTS channelbag path

[TMHSDigital]

Closes #385.

Problem

On 4.5 LTS, snippets/action-ensure-channelbag-for-slot.py wrote keys through the legacy action.fcurves.new() on a slotless Action. That creates a Legacy Slot but never assigns it, so animation_data.action_slot stays None, and the object never animates. No error is raised. The skill recommended the same legacy path.

Change

• Snippet:
  • binds the slot on both versions;
  • on 4.4/4.5 builds the layer/strip/channelbag path with strip.channelbag(slot, ensure=True), mirroring the skill's get_channelbag_for_slot;
  • the header now says why.
• Skill:
  • the legacy action.fcurves section now binds action_slot explicitly and documents the trap;
  • the cross-version intro and the compatibility table no longer recommend bare action.fcurves;
  • Mistake fix: remove paths-ignore from release.yml so content edits fire release pipeline #2 names the 4.5 legacy case.

Evidence

Proven by live run (--background --factory-startup; binaries report 5.2.1 LTS and 4.5.11 LTS from .scratch/):

Check	4.5.11 LTS	5.2.1 LTS
Snippet add_z_keyframe (f1=0, f24=2) → frame_set(24) z	2.0 (was 0.0 before the fix)	2.0
action_slot bound after the snippet	True (was None)	True
Skill legacy block (fcurves.new + explicit action_slot) → x at f24	5.0	n/a (action.fcurves removed in 5.0)

Falsification: the pre-fix snippet on 4.5.11 gave z = 0.0 and action_slot = None, which is the issue's measurement.

By inspection only: no CI example covers this snippet directly. The snippet is not in tests/smoke/catalog.json.

🤖 Generated with Claude Code

[TMHSDigital]

CI evidence on PR head: Blender Smoke ran 5.2.2 LTS (143 passed, 1 skipped, 0 failed) and 4.5.14 LTS (141 passed, 3 skipped, 0 failed); falsifier table 142/136 passed, 0 failed. Merging.