fix: handle pnpm --filter/-F flag (#259)

[ousamabenyounes]

Summary

Fixes #259 — rtk pnpm --filter mymodule test fails with "unexpected argument '--filter' found".

Root cause: pnpm's --filter is a global flag that precedes the subcommand (pnpm --filter <pkg> <cmd>). Clap's PnpmCommands subcommand enum expects a subcommand name first, so --filter is rejected as an unknown flag.

Fix: Intercept --filter / --filter= / -F in raw args before Cli::try_parse() and route directly to pnpm_cmd::run_passthrough().

Before/After

# BEFORE
$ rtk pnpm --filter mymodule test
error: unexpected argument '--filter' found
Usage: rtk pnpm [OPTIONS] <COMMAND>

# AFTER — all variants work
$ rtk pnpm --filter mymodule test     # ok
$ rtk pnpm --filter=mymodule test     # ok
$ rtk pnpm -F mymodule test           # ok

Impact

In pnpm monorepos (very common in modern JS/TS), almost every command uses --filter. Without this fix, every pnpm command in a monorepo bypasses RTK filtering = 0% savings instead of 70-90%.

Test plan

• New test: test_pnpm_filter_detected — verifies detection logic for all 3 variants
• Full suite: 765 passed, 0 failed
• Manual verification: --filter, --filter=, -F all pass through to pnpm
• cargo fmt && cargo clippy && cargo test all green
• validate-docs.sh passes

Generated with Claude Code

[pszymkowiak]

Hi! Thanks for the contribution! Since March 6, all PRs should target the develop branch instead of master (see CONTRIBUTING.md).

Could you update the base branch? Click Edit at the top right of this PR and change it from master to develop.

Thanks!

[ousamabenyounes]

Done sorry! :)