providers: duplicate & contradictory SELF_MANAGED_PROVIDERS (dead kokoro.py copy omits qwen3tts)

[thinmintdev]

Bug

Two definitions disagree:

• live: slots/state.py:124 frozenset({"kokoro","qwen3tts","moonshine","vibevoice"}) (re-exported via slots/__init__.py:20)
• dead: providers/kokoro.py:59 frozenset({"kokoro","comfyui"})

Nothing imports hal0.providers.kokoro.SELF_MANAGED_PROVIDERS (only tests + slots/__init__ import the symbol). The kokoro copy is unused and wrong (lacks qwen3tts/moonshine/vibevoice, wrongly includes comfyui). qwen3tts.py:36-37 docstring asserts qwen3tts is in the set — true for the live one, contradicted by the kokoro constant. A contributor reading kokoro.py would get the wrong answer.

Fix

Delete the dead SELF_MANAGED_PROVIDERS in kokoro.py:59 (and its docstring refs) so slots/state.py:124 is the single source of truth.

Acceptance criteria

• Constant removed from kokoro.py; imports unaffected
• Grep confirms slots/state.py is the only definition

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Filed from the v0.8.2b3 codebase assessment sweep; finding adversarially verified against HEAD (`chore/release-0.8.2b3`).