Tier-S: #43 sub — fuzz targets (7 → 20, +13)

[hyperpolymath]

Scope (sub-issue of #43)

Expand fuzz targets from 7 → 20 (+13).

Current targets (per fuzz/Cargo.toml): arith, glob, job_spec, parser, path_operations, signal_parse, state_machine.

Target axes (13 new)

Target	Surface
fuzz_quotes	quote-state machine corners
fuzz_redirect	redirect parsing (file/heredoc/process-sub)
fuzz_audit_log	JSON-line parser robustness
fuzz_obliterate	RMO payloads + extreme sizes
fuzz_function_definition	function-body parser corners
fuzz_pipeline_construction	pipeline-stage edges
fuzz_parameter_expansion	every ${VAR…} form
fuzz_arithmetic_evaluator	overflow, divide-by-zero, recursion
fuzz_alias_expansion	recursive alias detection
fuzz_history_replay	malformed .vsh_state.json
fuzz_glob_with_braces	brace-expansion combinatorics
fuzz_command_substitution	$(...) and backtick edges
fuzz_test_command	[, [[, test

Resolution

1. Each fuzz target → 1 PR.
2. ClusterFuzzLite already configured at .clusterfuzzlite/ (per PR docs+ffi: fill rsr-template placeholders left from template instantiation #59).
3. Each target needs Arbitrary derive + minimal initialization.

References

• Parent: Test + bench dramatic expansion — 736 → 2000+ tests, 3 → 15 benches, 7 → 20 fuzz targets #43