Derive endorsed_tcb dynamically from attestation report in SNP test

[Copilot]

The endorsed_tcb parameter in the SNP attestation test was hardcoded ("541700000000000a"), making it brittle across SNP hosts and processor architectures (Milan/Genoa/Turin) where the reported TCB varies.

Changes

• tests/npm_tests.py: Replace the hardcoded endorsed_tcb value with one derived from reported_tcb in the first verifySnpAttestation response. The first call (already present in the test) returns the attestation report containing reported_tcb — a hex string encoding the actual TCB for the running architecture. That value is then passed as endorsed_tcb in the second call.

# First call (no endorsed_tcb) — captures reported_tcb from the live attestation
report_json = r.body.json()["attestation"]

# Second call — uses the actual reported_tcb, correct for Milan/Genoa/Turin
endorsed_tcb = report_json["reported_tcb"]
r = c.post("/app/verifySnpAttestation", {
    ...,
    "endorsed_tcb": endorsed_tcb,
})

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