seed-oss: simplify parser and add content-only fallback
- Simplify eos/reasoning handling with p.space() and ternary
- Remove <seed:toolcall> typo fallback
- Add content-only fallback when tools provided but not called
- Handle missing <seed:eos> with optional content wrapper + p.rest() fallback
- Keep until_one_of patterns with newline variants (GBNF generation quirk)
- Comment out partial parsing test (needs more work)
- Enable seed_oss:experimental tests
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
