fix(weights): include netuid in BatchWeightItemFailed event

[RUNECTZ33]

Description

do_batch_commit_weights and do_batch_set_weights accept a list of (netuid, payload) pairs and forward each one to the per-item dispatch. When an item fails, the chain emits

Self::deposit_event(Event::BatchWeightItemFailed(err));

which carries the DispatchError but not the netuid that produced it. Downstream consumers (block explorers, validator monitors, indexers) watching a batch see that an item failed and what error variant fired, but cannot tell which subnet without re-deriving from iteration order — fragile across runtime upgrades and not available to event-only subscribers.

The call site already has netuid in scope at the time of emission, so plumbing it through is mechanical.

Fix

1. Change event signature:

   BatchWeightItemFailed(NetUid, sp_runtime::DispatchError)

2. Both emission sites in subnets/weights.rs now collect Vec<(NetUid, DispatchResult)> from the per-item map and emit BatchWeightItemFailed(netuid, err) for each failing item.
3. Bumps spec_version 406 → 407.

Shape mirrors #2614 ("Add netuid to TransactionFeePaidWithAlpha event") which made the same observability improvement on a different event.

Tests

Adds two regression tests in pallets/subtensor/src/tests/weights.rs. The batch-event layer had no prior coverage (grep on the test tree for either event returned no hits).

• test_batch_commit_weights_item_failure_event_includes_netuid — submits a 2-item batch where both items hit CommitRevealDisabled, asserts the emitted BatchWeightItemFailed events carry [netuid_a, netuid_b] in iteration order.
• test_batch_set_weights_item_failure_event_includes_netuid — same shape for the set-path, using CommitRevealEnabled as the failure trigger.

Both pass locally:

SKIP_WASM_BUILD=1 cargo test -p pallet-subtensor --lib -- \
  tests::weights::test_batch_commit_weights_item_failure_event_includes_netuid \
  tests::weights::test_batch_set_weights_item_failure_event_includes_netuid
running 2 tests
test tests::weights::test_batch_commit_weights_item_failure_event_includes_netuid ... ok
test tests::weights::test_batch_set_weights_item_failure_event_includes_netuid ... ok
test result: ok. 2 passed; 0 failed

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Breaking Change

The event signature is extended by one positional argument. Consumers that decode events by position (Polkadot.js Apps, indexer libraries, off-chain workers) will need to update their parsers — same compatibility surface as #2614. No on-chain storage change; no migration required.

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run ./scripts/fix_rust.sh to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix

Related

• Companion observability fix to PR Add netuid to TransactionFeePaidWithAlpha event #2614 ("Add netuid to TransactionFeePaidWithAlpha event")
• Open PR fix(coinbase): clear AutoStakeDestination on subnet dissolve #2652 (RUNECTZ33) — different bug class (orphan storage on dissolve); independent of this change

[open-junius]

looks good to me