feat(ci): attest build provenance #373

Job	Run time
Bridge — node (unit + boot smoke)	6s
Bridge — bun (unit + boot smoke)	10s
Detect relevant changes	5s
Bridge — deno (unit + boot smoke)	13s
Bench — mcp-bridge (path-claims)	0s
E2E — Order Ticket (FFI layer)	-1s
Aspect — Thread Safety + ABI Contract + SPDX	-1s
Bench — FFI Catalogue + Mount/Unmount + Hash	-1s
E2E — Full REST + MCP Bridge	-2s
	29s

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