feat: passthrough fallback when Clap parse fails

[guillaumedeslandes]

Summary

• When RTK cannot parse a command (e.g. rtk git -C /path status), instead of exiting with Clap error code 2, it now falls back to running the raw command directly
• Adds parse_failures SQLite table to track these events for analytics
• Adds rtk gain --failures (-F) to view failure log with recovery rate and top commands

Motivation

Clap calls std::process::exit(2) before main() executes when it can't parse args. This blocks developer workflows for commands RTK doesn't fully model (e.g. git -C, unknown flags). The fallback ensures RTK never breaks a command that would otherwise work.

Changes

File	Change
src/main.rs	Cli::parse() → try_parse() + run_fallback() with Stdio::inherit(), 7 tests
src/tracking.rs	parse_failures table, record_parse_failure(), get_parse_failure_summary(), silent wrapper, 2 tests
src/gain.rs	--failures / -F flag, show_failures() display function

Test plan

• cargo fmt --all --check passes
• cargo clippy --all-targets — 0 new errors
• cargo test --all — 387 tests pass
• rtk git -C . status — fallback works, prints [rtk: parse failed, running raw]
• rtk --help / --version — still work normally
• rtk gain --failures — shows failure log after fallback triggers

🤖 Generated with Claude Code

[pszymkowiak]

Tested locally — solid approach, needs rebase + 2 fixes before merge.

Testing results:

• 387/387 unit tests pass
• 82/83 smoke tests pass (1 fail due to branch being behind master)
• Manual testing confirms fallback works correctly for git -C, git --no-pager, grep -E
• Normal RTK-filtered commands (git status, git log, --help, --version) unaffected

Must fix:

1. Rebase on master — branch is 2 commits behind (missing v0.22.0/0.22.1), cargo test count mismatch
2. Guard RTK meta-commands from fallback — rtk gain --badtypo currently tries to execute a gain binary from $PATH before showing the Clap error. Add a check for known RTK-only subcommands
   (gain, discover, learn, init, config, proxy, hook-audit, cc-economics) and show the Clap error directly for those.

Nice to have (non-blocking):

• Timer starts after command completes — all fallback commands show ~0ms in rtk gain --history. Move TimedExecution::start() before the .status() call.
• parse_failures table never gets cleaned up (only record() calls cleanup_old(), not record_parse_failure())
• Strip ANSI codes from Clap error before storing in SQLite (utils::strip_ansi already exists)

This will fix #204, #228, #229 and any future unknown-flag issues globally. Great work!