starknet_transaction_prover,tower_ohttp: OHTTP-unlinkable request-id for decapsulated content

[avi-starkware]

Tags downstream content logs with a request-id via a new RequestSpanLayer
placed below the OHTTP layer. For plaintext it reuses the envelope id from
RequestLogLayer; for an OHTTP-decapsulated request (marked with a new
tower_ohttp::Decapsulated extension) it mints a FRESH UUID. Any
client-supplied inner x-request-id is stripped by tower_ohttp at
decapsulation time, so the property holds even if the marker is ever lost
(fail-closed).

The fresh inner id is never echoed back, so the relay-visible envelope id and
the gateway's content-log id share no join key — preserving OHTTP
unlinkability while still giving every request's downstream logs a
correlatable id. Both integration tests exercise the production
prover_http_middleware! chain, so a layer reorder that reverts either
property fails CI.

Co-Authored-By: Claude Opus 4.7 (1M context) noreply@anthropic.com

[reviewable-StarkWare]

This change is 

[avi-starkware]

• starknet_transaction_prover: log resolved config at startup (secrets redacted) #14684
• starknet_transaction_prover: document existing logging, request ids and health probe in README #14203
• starknet_transaction_prover: origin-level breadcrumbs for validation errors #14172
• starknet_transaction_prover: /health returns 503 when service is saturated #14171
• starknet_transaction_prover: bump prover_panics_total on panic hook fire #14170
• starknet_transaction_prover: HTTP request count + latency + in-flight metrics #14169
• starknet_transaction_prover: proving-job duration + outcome metrics #14168
• starknet_transaction_prover: Prometheus /metrics endpoint with build_info #14167
• starknet_transaction_prover: global panic hook with structured log #14166
• starknet_transaction_prover,tower_ohttp: OHTTP-unlinkable request-id for decapsulated content #14222 👈 (View in Graphite)
• starknet_transaction_prover: per-request structured log with request-id #14165
• starknet_transaction_prover: unify HTTP middleware stack via macro #14286
• main-v0.14.3

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[cursor]

PR Summary

Medium Risk
Changes OHTTP privacy behavior and HTTP middleware ordering on the transaction prover entry path; mistakes could leak join keys between relay and gateway logs, though stripping at decapsulation and new CI tests mitigate that.

Overview
Adds RequestSpanLayer below OHTTP in prover_http_middleware! so downstream http_request tracing uses a correlatable id without linking relay-visible envelope traffic to gateway content logs.

tower_ohttp strips inner x-request-id when rebuilding BHTTP requests, tags decapsulated inner dispatches with a Decapsulated extension, and documents that stripping is the fail-closed unlinkability guarantee if the marker is lost.

For plaintext, the span reuses the id from RequestLogLayer; for OHTTP-decapsulated requests it mints a fresh UUID on the inner request (discarding any client inner id) so it never matches the envelope id echoed on the outer response.

Integration tests run the real prover_http_middleware! chain (compression ordering and envelope vs inner id unlinkability); OHTTP integration tests share OHTTP_JSONRPSEE_BODY_BUILDER instead of duplicating the middleware stack.

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[Yoni-Starkware]

@Yoni-Starkware reviewed 8 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on einat-starkware).

[gkaempfer]

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