Batch sender fixed

[stpatrickghost]

Summary

Batch-sender was emitting single-topic ANNOUNCE events, which broke
server-side topic-3 view-tag filtering and forced indexers to full-scan
its output. Per-transfer announcements now go through the announcer
contract, the same announcer_client::announce pattern splitter already
uses, so all three sources emit the v2 4-topic layout:

topics: ("announce", scheme_id, view_tag_bucket, metadata_kind)
data: (stealth_address, ephemeral_pub_key, metadata)

view_tag_bucket = metadata[0] as u32.

Issue #62 is an audit-doc correction only. splitter fund_split already
routes through the announcer; no splitter logic change.

Changes

• stealth-batch-sender: drop inline (ANNOUNCE,) publish; call announcer
  instead. batch_send now takes announcer + scheme_id. Transfer gains
  metadata and uses BytesN<32> for the ephemeral key.
• Unit + snapshot tests assert the 4-topic layout and view-tag derivation.
• New integration test topic_filter.rs: topic-3 filter returns only the
  matching view-tag subset across announcer, splitter, and batch-sender.
• EVENT_INDEXING_AUDIT.md: close Per-network deployment config validation #63 as resolved; close Independent third-party audit preparation pack #62 as a stale
  audit-doc finding.
• Reference indexer processor: one announcement path for announcer,
  sender, splitter, and batch-sender. No batch-sender-specific
  single-topic handler.
• bench-crossover and Cargo.toml/lock updated for the new API.
• stealth-splitter Cargo.toml adds rlib so the integration test can
  link it. No splitter source change.

Test plan

• cargo fmt --all -- --check
• cargo test -p stealth-batch-sender
• cargo test -p integration-tests --test topic_filter
• cargo check -p stealth-batch-sender -p integration-tests -p stealth-splitter -p wraith-stellar-bench-crossover

Closes #159

[truthixify]

Thanks for reopening this @stpatrickghost, and the cargo fmt drift from before is gone.

The stellar job now fails on something else, and it is not in batch-sender:

error[E0432]: unresolved import `wraith_metrics`
 --> stealth-splitter/src/lib.rs:7:5
7 | use wraith_metrics::{contract_ids, dimension_names, emit_metric, metric_names};

That import arrived with #171 (metrics wiring), which also added the matching dependency to stellar/stealth-splitter/Cargo.toml. Current develop has both halves and compiles fine. Your branch has the .rs half without the Cargo.toml half, which is the signature of a rebase or merge that took one side of a conflicted file.

Rather than patching the Cargo.toml by hand, rebase cleanly so you pick up both:

git fetch origin
git rebase origin/develop

Then confirm stellar/stealth-splitter/Cargo.toml contains wraith-metrics = { path = "../wraith-metrics" } under [dependencies] before pushing.

One small thing in your own diff: stellar/stealth-batch-sender/Cargo.toml gains a trailing whitespace line and loses its final newline. Harmless, but cargo fmt will not catch it, so worth tidying while you are there.