fix: keep claude_args flags when the block opens with a comment line

[MuhammadMehroz786]

Fixes #1892

Problem

stripShellComments (base-action/src/parse-sdk-options.ts) only drops a # comment that starts its own line. Tag mode and agent mode, however, append the user's claude_args to their own flag line with a space:

claudeArgs += ` ${userClaudeArgs}`;                  // src/modes/tag/index.ts
claudeArgs = `${claudeArgs} ${userClaudeArgs}`.trim(); // src/modes/agent/index.ts

When the block opens with a comment line, that comment no longer starts a line of the joined string, so it survives stripShellComments, and shell-quote treats everything from the # to the end of the string as one comment, newlines included. Every user flag is silently lost and the run proceeds on the action's defaults. Meanwhile parseAllowedTools tokenizes the user's block on its own, so the inline-comment server is still installed while the SDK never receives --allowedTools (the disagreement parse-tools.ts says to avoid, #1357).

Reproduced through parseSdkOptions on the current main:

space join:   model undefined, maxTurns undefined, extraArgs { "permission-mode": "acceptEdits" }
newline join: model "opus",    maxTurns 120,       extraArgs { "permission-mode": "acceptEdits", "strict-mcp-config": null }

Fix

Join the user's block on a newline instead of a space in both modes. The user's first line is then always its own line, so a leading full-line comment is stripped exactly like one anywhere else in the block. shell-quote already treats a newline as whitespace between tokens, and the joined string goes straight from prepareResult.claudeArgs to runClaude in-process, so nothing else on the path needs to change.

Tests

Added one test per mode that sets CLAUDE_ARGS to a block opening with a comment line, runs the mode's prepare*, and feeds the result through parseSdkOptions. Both fail on main (model comes back undefined) and pass with the fix.

• bun test: 968 pass, 0 fail
• bun run typecheck: clean
• bun run format:check: clean

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