feat(run): support -- passthrough for app arguments

[mattleibow]

Summary

Adds support for the -- passthrough separator in winapp run, so users can pass flags to their launched app without escaping:

# Before (requires escaping)
winapp run . --args "--my-flag value"

# After (no escaping needed)
winapp run . -- --my-flag value

Tokens after -- are collected and merged with any --args value. Unknown tokens before -- are still caught and reported as errors (e.g. typos like --detch).

tool and store already used TreatUnmatchedTokensAsErrors = false — no changes needed for those.

Changes

• RunCommand.cs: Set TreatUnmatchedTokensAsErrors = false, collect post--- tokens, count-based pre-dash validation, merge with --args
• RunCommandTests.cs: 14 tests covering parse-level behaviour, handler happy paths, rejection, and mode interactions (--no-launch, --detach, --debug-output)
• docs/usage.md + docs/fragments/skills/winapp-cli/setup.md: Updated examples

Test coverage

Area	Tests
Parse: bare --, no parse errors for unknown pre-dash tokens	3
Handler: bare --, multiple args, merge with --args, space-quoting	4
Handler rejection: unknown option, same-value duplicate bug case	3
Mode interaction: --no-launch, --detach, --debug-output	3

All 57 RunCommand tests pass.

[Copilot]

Pull request overview

Adds -- passthrough support to winapp run so users can forward application arguments without needing to escape/quote them into --args, while still rejecting unknown winapp run options typed before the separator.

Changes:

• Updated run command parsing to allow unmatched tokens, collect tokens after --, validate unknown tokens before --, and merge passthrough tokens with --args.
• Added a new test region covering parse behavior, handler forwarding/merging, rejection of unknown options, and interactions with other run modes.
• Updated docs to describe and demonstrate the new -- passthrough usage.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
src/winapp-CLI/WinApp.Cli/Commands/RunCommand.cs	Enables unmatched tokens for run, collects/validates passthrough args after --, merges with --args.
src/winapp-CLI/WinApp.Cli.Tests/RunCommandTests.cs	Adds coverage for -- passthrough parsing and handler behavior across modes.
docs/usage.md	Documents -- passthrough as an alternative to --args and adds an example.
docs/fragments/skills/winapp-cli/setup.md	Adds setup documentation example showing passthrough usage.

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[mattleibow]

Note: ToolCommand argument escaping

ToolCommand.cs currently uses a naive space-quoting approach for tool arguments:

Arguments = string.Join(" ", toolArgs.Select(a => a.Contains(' ') ? $"\"{a}\"" : a))

This has the same embedded-quotes / trailing-backslash issue documented in earlier review comments. The correct fix is to switch to ProcessStartInfo.ArgumentList:

foreach (var arg in toolArgs)
    processStartInfo.ArgumentList.Add(arg);

ProcessStartInfo.ArgumentList (available since .NET 5) lets the BCL handle CommandLineToArgvW-compatible escaping internally — there's no need to call WindowsCommandLine.EscapeArgument since we're launching a real process (not going through COM).

This was intentionally left out of the current PR to keep scope focused on the run command passthrough feature. Tracked as a follow-up improvement.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

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