add timeout-without-lockin and variant detection examples (#108, #109)

[neverDefined]

Summary

Closes Phase 6.1. Two final worked examples plus a small validation hardening of time.go that surfaced during development.

TestExampleTimeoutWithoutLockin (closes #108)

Narrated mirror of TestExampleActivateTestdummy for the BIP9 FAILED path. Uses WarpTime to drag MTP past a configured timeout, then mines to the second retarget boundary where Bitcoin Core evaluates STARTED → FAILED.

Two non-obvious recipe details surfaced and are documented inline:

• Signaling-vs-timeout precedence. Core's BIP9 checks the signaling threshold before the timeout check, and regtest's default block-version policy signals every STARTED deployment automatically. Without intervention, testdummy would LOCKED_IN before timeout could fire. The test passes -blockversion=0x20000000 (BIP9 baseline with no deployment bits set) via ExtraArgs to suppress signaling so the FAILED path is reachable.
• uint32 block-timestamp cap. Block headers store nTime as uint32, max 4_294_967_295 (year 2106). Setting mocktime above this cap causes generatetoaddress to fail with a cryptic time-too-old error (the value overflows). The test uses timeout = 4_000_000_000 (year 2096) — comfortably under the cap.

Skips on Inquisition, where testdummy is a heretical deployment that isn't -vbparams-overridable.

TestVariantDetection (closes #109)

Smoke test that Variant() resolves to VariantCore or VariantInquisition (not the zero-value VariantUnknown — that would indicate a getnetworkinfo.subversion parser regression). Logs the detected variant and binary path so CI output records which build the suite ran against.

time.go — uint32 cap validation

Surfaced by the timeout test work. Added maxBlockTime constant (4_294_967_295) and validation:

• MineWithTimestampContext rejects unix > maxBlockTime up front with a clear message.
• WarpTimeContext rejects target > maxBlockTime up front.

Both methods' godoc updated. Existing SetMockTime keeps the looser maxMockTime = 9_223_372_036 cap (matches Core's RPC validation) since you can call setmocktime for non-mining purposes.

Test plan

• make ai-check green (against bitcoind-inquisition on PATH).
• TestVariantDetection passes on Inquisition (logs running against variant: inquisition).
• TestExampleTimeoutWithoutLockin t.Skips cleanly on Inquisition.
• On Core (verified via temporary BinaryPath-override probe): TestExampleTimeoutWithoutLockin runs to completion with final status: failed. Probe was deleted before commit.

Notes

• Closes Phase 6.1 milestone. With add layered time API: SetMockTime, MineWithTimestamp, WarpTime (#103, #104, #105) #115 merged and this PR, all 13 issues across both Phase 6 milestones ([Phase 6.A.1] Config.BinaryPath + script env-var indirection #97–[Phase 6.E.4] TestVariantDetection smoke test #109) are closed. Tracking issue [Phase 6] Inquisition + time-warp roadmap (tracking) #110 can be closed too.
• The -blockversion workaround is regtest-only (MineBlocksOnDemand() gates the override). On mainnet/testnet it's a no-op.

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