build: omit debug info from ordinary release builds

[shinaoka]

Summary

Follow up merged PR #581 by changing ordinary release builds from line-tables-only to debug = 0. Keep the existing full-debug release-debug profile for Tensor4all.jl/C API source-level diagnostics and debugger sessions.

Fixes #585.

Measured effect

Controlled full-workspace cold builds from the same PR #581 commit and lockfile:

Profile	Allocated target	Wall time	ELFs with .debug_*
line-tables-only	14,759,100,416 B	478.01 s	206 / 206
debug = 0	3,354,374,144 B	456.98 s	0 / 206

Allocated output decreased by 11,404,726,272 bytes (77.27%). The C API shared library decreased from 118,446,592 to 23,072,104 bytes.

Changes

• Set ordinary [profile.release] debug = 0; dev/test were already zero.
• Retain [profile.release-debug] debug = true.
• Document cargo build --profile release-debug -p tensor4all-capi plus RUST_BACKTRACE=1 for source-level Rust diagnostics.
• Add durable build-profile design and measurement worklog.

Optimization, numerical behavior, public APIs, C ABI, feature selection, assertions, and overflow behavior are unchanged. Ordinary backtraces may omit source file/line information; the explicit diagnostic profile preserves the prior full behavior.

Verification

• Cargo metadata/tree parsing — passed
• cargo fmt --all -- --check — passed
• cargo clippy --workspace --all-targets -- -D warnings — passed
• cargo nextest run --release --workspace — 2524 passed, 14 skipped
• cargo test --doc --release --workspace — 117 passed
• cargo doc --workspace --no-deps — built (pre-existing rustdoc link warnings remain)
• ./scripts/test-mdbook.sh — passed with the repository-standard target directory
• ordinary tensor4all-capi release ELF — no .debug_*
• release-debug C API ELF — full .debug_* present
• repository-rules review — pass, no findings

An initial mdBook invocation with an externally overridden CARGO_TARGET_DIR failed because the existing script intentionally resolves $repo_root/target/release/deps; rerunning the prescribed command without that unrelated override passed. No source fix was needed.

Documentation

• docs/design/build-profiles.md
• docs/worklogs/2026-08-09-release-debug-info-reduction.md

Related: PR #248, PR #581, tensor4all/tensor4all-agent-rules#9.

[github-actions]

Repository rules review

Repository rules review (bf6ee400e5903034f4b9f0b0da854f53b67e3cb8...2ea7457acf2f32ca2de4474d6f81690f09422784)
Verdict: pass
LLM review: 1 chunk(s) (11310 chars) in 10.5s; 0 finding(s) returned, 0 kept, 0 dropped by diff-anchor filtering.
No findings.