feat(chainspec): hardcode Longevity testnet hardfork timestamps

[nekomoto911]

Summary

• Longevity testnet (chain id 7771625) hardfork timestamps become binary-authoritative, like mainnet already is. A testnet node now schedules Prague, Osaka, Alpha, Beta, Gamma, TestnetOwnerFix and TestnetOwnerFixV2 at the on-chain activation timestamps regardless of its genesis file.
• Why: testnet times were per-node genesis input and the repository copy had already drifted — genesis/testnet/genesis.json lacks testnetOwnerFixV2Time, so a node started from it would never schedule TestnetOwnerFixV2 and would diverge replaying block 32664162. Target release: v1.10.1 (next testnet upgrade).

Architecture and Key Decisions

• Extends the existing HARDCODED override table in bin/gravity_node/src/chainspec.rs; no new mechanism. The table now covers every Gravity key greth reads from genesis: alphaTime, betaTime, gammaTime, testnetOwnerFixTime, testnetOwnerFixV2Time (plus typed prague_time / osaka_time). The duplicated per-key blocks in apply_overrides are folded into one loop; event format and order are unchanged, new keys report after betaTime.
• Every hardcoded timestamp (mainnet and testnet, mainnet Prague included) is a named constant in the new bin/gravity_node/src/fork_times.rs, documented with its date, activation block and observed effect; the HARDCODED table only references constants. Pin tests keep literal values as the independent check.
• Testnet chain id comes from greth's LONGEVITY_TESTNET_CHAIN_ID.
• Mainnet pins the three new keys to absent. OwnerFix keys are inert on mainnet anyway (greth chain-id gate); Gamma has no chain-id gate, so this prevents a genesis gammaTime from activating Gamma on a single mainnet node before the mainnet time is pinned.
• Genesis files are not edited: once hardcoded, genesis fork fields no longer drive behavior.
• TestnetGammaBridge is intentionally not included; it lands with the greth bump that implements it.

Activation evidence (public testnet RPC, 2026-09-30): for each value, the first block with timestamp >= value has its predecessor one second earlier, and the fork's state effect appears in that block.

Fork	Timestamp	First block	Observed effect
Prague	1780909442	1084564	EIP-2935 history contract code appears
Alpha	1783328400	10787823	matches greth #442
Beta / Osaka	1785812400	—	no observable state effect; live genesis value
Gamma	1787108400	25666608	NativeOracle runtime swapped (4602 → 3904 bytes)
TestnetOwnerFix	1788490800	30922944	StakePool pendingOwner set
TestnetOwnerFixV2	1788948000	32664162	pendingOwner set to cast-derived address

Risks and Remaining Work

• Beta/Osaka rest on the live genesis snapshot, not a state observation.
• Replay of testnet and mainnet state with the v1.10.1 binary remains a release gate.
• Testnet nodes whose genesis lacks testnetOwnerFixV2Time log one WARN [GravityChainSpecParser] ... binary forces testnetOwnerFixV2Time = 1788948000; genesis says <unset> line at startup and run normally.
• Pre-existing, not addressed: cargo clippy -p gravity_node with dependencies fails on crates/api FailpointConfResponse dead code under -D warnings.

Breaking Changes

None. Hardcoded values equal on-chain activations; live mainnet genesis (SDK and gravity-mainnet-gitops) has none of the three new keys, so mainnet schedule and startup output are unchanged.

Database Migrations

None.

Verification

• RUSTFLAGS="--cfg tokio_unstable" cargo test -p gravity_node → 57 passed (38 in chainspec), re-run after the fork_times.rs move. The new testnet tests were observed failing before the testnet entry existed; repository_testnet_genesis_never_contradicts_table failed with TestnetOwnerFixV2: left Never, right Timestamp(1788948000).
• cargo +nightly-2026-09-05 fmt --all -- --check → clean.
• RUSTFLAGS="--cfg tokio_unstable" cargo clippy -p gravity_node --no-deps --all-targets --all-features -- -D warnings → clean.
• E2E not required: pure genesis → ChainSpec transform proven at the parser boundary with the real repository testnet genesis; the startup funnel is unchanged.

Merge Order

None.

Related PRs

None.