ipc: add TritRPC frame pack operation

[mdheller]

Summary

Adds tritrpc.frame.pack to the IPC v0 TritRPC bridge adapter.

What lands

• reference/ipc-v0/tools/run-tritrpc-frame-pack-check
• reference/ipc-v0/fixtures/payload-addvertex-a.json
• reference/ipc-v0/tests/test_tritrpc_frame_pack_check.py
• bridge adapter support for tritrpc.frame.pack
• reference/ipc-v0/tests/test_tritrpc_frame_pack_op.py
• README documentation for dry-run and execute-mode frame packing

Why

Fixture verification is now available through IPC. This PR adds the sibling frame-pack operation using the selected Rust CLI codec wrapper path.

Boundary

• default mode is dry-run argument validation
• execute mode requires explicit local trpc path
• no fixture fetch
• no fixture byte vendoring
• no network transport
• key material is redacted in receipts

Follow-on

• add execute-mode CI once a stable local TriTRPC CLI provisioning path is accepted
• add frame output comparison against a selected canonical vector