Serialize the name-tagger automaton to cut first-use latency (~1.5s build -> ~7ms load)

Summary

The name tagger's Aho-Corasick automaton is rebuilt from its full needle set on the first analyze_names(..., symbols=true) call of every process. That build is ~1.5s and is the dominant cost of first use / cold start. It is cached for the process lifetime afterward (the Tier 1 LazyLock<AhoCorasick>), so it is purely a startup cost.

plans/arch-rust-core.md already calls this out and names the fix:

aho-corasick v1 exposes no serde or raw-byte serialisation, so the build is from-source. If startup cost ever matters, daachorse (double-array AC with explicit serialisation) is the escape hatch.

This issue is that escape hatch, with measurements showing startup cost does matter (it dominates cold start in serverless / short-lived-process deployments) and that the win is large.

Prototype and numbers

Swapping aho-corasick for daachorse (double-array Aho-Corasick, supports zero-copy de/serialization) on the person tagger's needle set, release build:

Overlapping-search results are byte-identical to the current aho-corasick output across a set of probe haystacks. Net: the ~1.5s runtime build becomes a ~7ms load (plus faulting/decompressing the embedded artifact), with output unchanged.

A note on size: the deduped needle count actually fed to the automaton measured ~470k (470,083 unique forms from 564,529 aliases). arch-rust-core.md estimates Tier 1 at ~150k patterns, which appears to count corpus lines/groups rather than the expanded, deduped per-form needle set.

On the rejected-formats list

arch-rust-core.md rejects bincode / postcard / rkyv with "zero-copy gains are irrelevant after init." That reasoning targets the small Tier-2/3 data and the steady state. The daachorse gain here is different: it removes the ~1.5s automaton build, which is paid at init. That is the "if startup cost ever matters" case the same doc explicitly carves out for daachorse, not the post-init zero-copy case that was rejected.

Scope and open questions (would want maintainer input before a PR)

• Engine swap: aho-corasick -> daachorse in names::matcher::Needles, or a serialized fast path alongside it. daachorse is case-sensitive; rigour already pre-normalizes (CASEFOLD) both needles and haystack, so the current ascii_case_insensitive(true) is belt-and-suspenders, but full-suite parity needs verifying.
• Where to serialize: build.rs cannot call the crate's own builder, so it would need a small gen step / workspace member (or genscripts/), or committing the serialized artifact.
• Flag-keyed cache: precompute only for the default Normalize flags; other flag combinations fall back to a runtime build.
• Artifact size: ~25.7 MB raw (zstd-compressible like the existing corpus), embedded in the wheel.

Happy to implement this as a PR if the approach sounds reasonable. Prototype bench is available.

Start with plans/arch-rust-core.md and the names::matcher::Needles implementation, then inspect build.rs and the available prototype benchmark. Work out how the default Normalize configuration can load a serialized daachorse artifact while other flag combinations retain a runtime build. Done means the startup path is reduced toward the reported ~7 ms and overlapping-search output remains byte-identical across the full suite.