`bitcoin_core_sv2`: JDP stale-chain-tip detection should use `prev_hash` only (avoid `min_ntime`/`nbits`/`bip34` drift)

[plebhash]

DeclareMiningJob stale classification currently treats any validation-context drift as stale (prev_hash, nbits, min_ntime, bip34):

sv2-apps/bitcoin-core-sv2/src/unix_capnp/v31x/job_declaration_protocol/handlers.rs

Lines 289 to 321 in 453e853

	} else {
	let stale_at_arrival_by_bip34 = declared_bip34_height != latest_bip34_height;
	let context_drifted = initial_validation_context.prev_hash
	!= latest_validation_context.prev_hash
	|| initial_validation_context.nbits != latest_validation_context.nbits
	|| initial_validation_context.min_ntime != latest_validation_context.min_ntime
	|| initial_bip34_height != latest_bip34_height
	|| stale_at_arrival_by_bip34;
	let error_code = if context_drifted {
	debug!(
	initial_prev_hash = ?initial_validation_context.prev_hash,
	initial_nbits = ?initial_validation_context.nbits,
	initial_min_ntime = initial_validation_context.min_ntime,
	initial_bip34_height,
	declared_bip34_height,
	latest_prev_hash = ?latest_validation_context.prev_hash,
	latest_nbits = ?latest_validation_context.nbits,
	latest_min_ntime = latest_validation_context.min_ntime,
	latest_bip34_height,
	stale_at_arrival_by_bip34,
	"Detected stale chain tip during DeclareMiningJob validation; classifying error as stale-chain-tip"
	);
	ERROR_CODE_DECLARE_MINING_JOB_STALE_CHAIN_TIP
	} else {
	ERROR_CODE_DECLARE_MINING_JOB_INVALID_JOB
	};
	JdResponse::Error {
	error_code,
	validation_context: latest_validation_context,
	}
	};

This can misclassify errors:

• min_ntime can increase without a tip change
• nbits/bip34 comparisons are unnecessary for stale-tip detection in this path

Stale tip classification should be restricted to mismatching prev_hash only.

---

Finally, there's no need for force_update_mempool_mirror to call createNewBlock().

Calling getTip() should be sufficient.

---

Note: this should be done on all versions, not only v31x (as could be implied by the code snippet above).