v0.2.0 — The reality sandwich (2026-08-19)

First real (non-simulated) evidence acquisition, causally sandwiched between live
proof-of-work blocks. Normative construction: docs/REALITY-SANDWICH.md.

B0  = 00000000fc80fe4f…  height 221   (the v0.1.1 live-anchor block itself)
        ≺  acquisition: 10 real NTPv4 exchanges, 5 independent operators
           (NIST, PTB, Google, Microsoft, Apple), challenge nonce embedded in
           every request and echoed by every server
        ≺
C   = 0000000055cddf6e…  height 222   (epoch-1 checkpoint payload, real difficulty-1 work)

New in this release:

• ctp/sandwich.py — challenge/nonce derivation, NTP witness profile with
  deterministic measurement re-derivation from raw packets, declared-origin
  picosecond frames (SPEC §3), integer-only IAU-2000 ERA expectation
  (EXPECTATION_NOT_EVIDENCE), sandwich bundle format, and the offline verifier
• scripts/run_sandwich.py / build_sandwich_template.py /
  assemble_sandwich_bundle.py / verify_sandwich.py
• tests/test_sandwich.py — derivation vectors, measurement math, and a full
  synthetic sandwich round-trip with tamper cases (suite: 25 tests)
• vectors/valid/reality-sandwich-bundle.cbor — the real sandwich, offline-verifiable

The epoch-1 checkpoint chains to the sealed epoch-0 checkpoint through its record
commitment. The consensus interval from the five witnesses is ±42 ms wide; the causal
window is one block on each side — the tightest this chain can express. The sandwich
proves when the evidence was acquired, never that its content is true; every
non-claim in the normative document applies.

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