feat: fix bindings stderr, agent prompt, jq 1.8, awk --csv

[chaliy]

Summary

• fix(bindings): Surface pre-exec failures (parse errors) in stderr for Python and JS bindings — previously only populated the error field, leaving stderr empty. Fixes bug(bindings): pre-exec failures disappear from stderr in Python/JS integrations #606, supersedes fix(bindings): surface pre-exec failures in stderr for Python/JS #625.
• docs(tool): Add operational guidance to the agent-facing system prompt: bash-vs-sh semantics, source usage, chunked multi-file writes, and configured limits. Fixes docs(tool): teach agents bash-vs-sh semantics and recommend chunked multi-file writes #608.
• feat(jq): Bump reported version from jq-1.7.1 to jq-1.8. Add tests for trim, ltrim, rtrim, abs, and if without else (jq 1.8 features supported by jaq 2.2.1). Addresses feat(jq): Upgrade jaq crates to 2.3.x and bump reported version to jq-1.8 #616.
• feat(awk): Implement --csv / -k flag with RFC 4180 field splitting (quoted fields, embedded commas, double-quote escaping). Sets FS="," and OFS="," in CSV mode. Fixes feat(awk): Add --csv flag for native CSV parsing #618, addresses feat(awk): Consider gawk 5.3+ features (CSV, Unicode escapes) #617.

Test plan

• All 8 new awk CSV tests pass
• All 6 new jq 1.8 tests pass (version, abs, trim, ltrim, rtrim, if-without-else)
• Tool system prompt test verifies bash-vs-sh guidance and limits surfacing
• cargo fmt --check clean
• cargo clippy --all-targets --all-features -- -D warnings clean
• cargo test --all-features passes (2 pre-existing doctest failures in realfs unrelated)