fix(cli): bound clap frame size by splitting oversized subcommand enums (Refs #215)

[noahgift]

Fixes #215.

It is not recursion

The issue originally guessed "deep recursion in the bash parser." Wrong — corrected on the issue. gdb shows six frames, no cycle:

#2 args::Commands::augment_subcommands                 (27 variants)
#1 args_corpus::CorpusCommands::augment_subcommands    (73 variants)
#0 args_corpus_analysis::CorpusAnalysisCommands::augment_subcommands (63)  ← crash

The failing test only calls Cli::parse_from(vec!["rash","check","test.rs"]).

Why the frames are huge

Per clap_derive-4.6.4 gen_augment, the body is a flat sequence with one new binding per variant:

let __clap_app = __clap_app.subcommand({ ...variant N... });

At opt-level 0 each binding gets its own uncoalesced stack slot and clap::Command is large. Measured ~12KB/variant: deleting the 63-variant flatten moved the requirement 2816KB → 2048KB.

The fix

Bound variants per generated function. clap emits #[command(flatten)] children as sequential calls, so peak = parent + max(child), not parent + sum — and flatten adds no CLI nesting. The repo already used this pattern (CorpusAnalysisCommands was split out of CorpusCommands the same way).

enum	before	after
CorpusCommands	73	5 shell + 23/24/24
CorpusAnalysisCommands	63	3 shell + 21/21/21

Results (with [profile.test] opt-level left at 0)

	before	after
stack required	2816KB	1664KB
margin vs 2MB budget	−768KB	+384KB
cli::tests	SIGABRT	13 passed
full suite	aborts	14593 passed, 0 overflows

opt-level = 1 also hides the symptom, but it compensates instead of removing the cause, and that profile's own comment flags coverage sensitivity. This split holds at any optimization level.

CLI surface is unchanged — the whole point

Diffed the full raw --help text of every node against a pristine build of HEAD:

3286 lines across 208 subcommand nodes — byte-identical.

Known unrelated failure

test_cov_keyring_init_with_import (a tempdir write race) fails in the full suite — and reproduces identically on pristine HEAD, verified by differential run. Not from this change.

Once this ships, the RUST_MIN_STACK=16777216 workaround in paiml/infra#170's clean-room gate can be removed.

🤖 Generated with Claude Code