feat: unify TFILLPAD modes and FP operand forms

[HecreReed]

Summary

• Collapse pto.tfillpad_inplace and pto.tfillpad_expand into pto.tfillpad with a mode attribute defaulting to normal.
• Remove the textual IR ops pto.textract_fp, pto.tinsert_fp, pto.tmov.fp, and pto.tstore_fp; represent FP variants through optional fp operands on pto.textract, pto.tinsert, pto.tmov, and pto.tstore.
• Keep one-to-one PTO-ISA lowering: no-mode FP forms select TEXTRACT_FP, TINSERT_FP, TMOV_FP, and TSTORE_FP, while explicit A5 acc-to-vec modes select the unified PTO-ISA overloads.
• Preserve PTO-BC v0 cross-build readability: existing canonical opcodes retain their fixed payload schemas, historical FP opcodes remain wire-only aliases that decode into the unified IR ops, and newer pre-quant forms use generic v0 encoding when they do not fit the shipped compact schema.
• Migrate Python bindings, PTODSL, TileLib, tests, samples, documentation, and PTOBC metadata.
• Update all seven managed PTO-ISA pin locations to 27386d906e8fdcbd93aec84197939bc0b2c6caea; extend update_pto_isa_pin.py and its workflow to cover ci_sim.yml and the compile-only guide.

Compatibility

• pto.tfillpad keeps source compatibility through mode = normal by default.
• Removed FP textual op names require migration to the corresponding unified op with an optional fp operand.
• PTO-BC v0 is treated as a cross-build exchange format. Opcode payloads assigned in v0 must not change without a version bump; legacy FP bytecode remains readable and is normalized during decode.

Validation

• PTOASPythonPackage build passed.
• Focused lit suite: 21 passed.
• PTODSL: 44 vector/cube tests and 37 TileLib tests passed.
• FP samples: Extract 2, TInsert 2, Movfp 2, Storefp 1 passed; invalid Storefp XFAIL behaved as expected.
• PTOBC suite: 20/20 passed, including old-schema static checks, FP opcode byte assertions, roundtrip decode, reparsing, and verifier checks.
• PTO-ISA pin verifier passed for all seven locations.
• git diff --check and removed-op residue checks passed.

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