chore(parser_app): address PR #303 follow-up review comments

[shahan-khatchadourian-anchorage]

Summary

Addresses all four follow-up items prasanna-anchorage raised on his approval of #303 (the per-PR narrow-build-check + local feature-matrix-check work). Single PR — all items are small, touch the same Makefile, and don't depend on each other.

Changes

1. Restore dynamic chain discovery ($(sort) + $(wildcard)).

PARSER_APP_CHAINS := $(sort $(patsubst visualsign-%,%,$(notdir $(wildcard chain_parsers/visualsign-*))))

The hardcoded list from #303 required editing both the Makefile variable and parser_app/Cargo.toml's [features] block whenever a chain was added. The sorted wildcard gives the same stable, deduplicated ordering the depth-2 pair generator needs, and the matrix auto-extends when a new chain_parsers/visualsign-<name>/ lands.

2. cargo build → cargo check in both targets.
The regression class these targets guard — unconditional chain-crate references that should have been #[cfg]-gated — is compile-level. cargo check is sufficient and roughly 2× faster than cargo build; the clippy invocations already cover lint coverage. As a bonus, feature-matrix-check now grows the target dir by ~2GB instead of ~28GB across its 31 invocations.

3. Add empty + diagnostics combo to feature-matrix-check.
--no-default-features --features diagnostics (no chains compiled in) makes the diagnostics axis symmetric with the rest of the matrix.

4. Tighten comments.

• narrow-build-check comment now reflects the auto-pickup behavior the dynamic variable provides.
• CI cache note rewritten to be accurate: parser_app re-type-checks under each distinct feature set while workspace dependencies are reused from earlier CI steps' cache.

Test plan

• make -C src narrow-build-check — 6 cargo check + 6 clippy invocations, exit 0.
• make -C src feature-matrix-check — 31 cargo check invocations (1 diagnostics-only + 5 singles + 5 singles+diagnostics + 10 pairs + 10 pairs+diagnostics), exit 0. Cargo target dir grew by ~2GB.
• Pre-commit hook (cargo fmt + cargo clippy across all workspace splits): clean.

References

• PR ci(parser_app): wire narrow-build-check; add local-only feature-matrix target #303 (merged): ci(parser_app): wire narrow-build-check; add local-only feature-matrix target #303
• prasanna-anchorage's approval comment with the follow-up asks

[Copilot]

Pull request overview

This PR updates the parser_app feature-gating verification targets in src/Makefile to be more maintainable and faster, addressing follow-up review items from PR #303.

Changes:

• Restore dynamic chain discovery for PARSER_APP_CHAINS via $(wildcard) + $(sort) so new chain_parsers/visualsign-*/ directories are auto-included.
• Switch narrow-build-check and feature-matrix-check from cargo build to cargo check to reduce runtime and disk usage while still catching compile-level feature-gating regressions.
• Extend feature-matrix-check to include a --no-default-features --features diagnostics (diagnostics-only, no chains) combo and tighten comments to reflect current behavior/CI caching.

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[prasanna-anchorage]

Approving — all four follow-ups from my #303 review are correctly addressed, and I verified each:

1. Dynamic chain discovery — $(sort $(patsubst visualsign-%,%,$(notdir $(wildcard chain_parsers/visualsign-*)))) expands to exactly ethereum solana sui tron unspecified, identical to the old hardcoded list, and parser_app's [features] block has a matching feature per chain. The $(sort) gives the stable, deduped ordering the pair generator needs. The "add a chain crate without wiring its feature -> fails loudly at narrow-build-check" behavior is exactly what I wanted.
2. cargo build -> cargo check — correct: the regression class (unconditional, un-cfg-gated chain-crate refs) is compile-level, so check is sufficient and clippy still covers the lint axis. Nice target-dir savings too.
3. diagnostics-only combo — verified cargo check -p parser_app --no-default-features --features diagnostics compiles locally; makes the diagnostics axis symmetric. Invocation count math checks out (31 = 1 + 5 + 5 + 10 + 10).
4. Comments — accurate now, including the CI-cache note.

No conflicts with main, CI green.

Non-blocking nit: the new standalone echo "==> features: diagnostics" line isn't @-prefixed, so make echoes the echo command itself before running it. Harmless and roughly consistent with how these targets already surface their cargo lines, but @echo would be tidier. Fine to leave.

LGTM.