fix(cli): catch output directory creation errors in render

[miguel-heygen]

Summary

• mkdirSync for the render output path was not wrapped in try-catch
• When the path was invalid or permissions were denied, Node.js threw a raw EACCES error with full stack trace
• Now catches the error and displays a clean error box via the existing errorBox helper

Reproducer

npx hyperframes render --output /root/nope/output.mp4
# Was: raw "Error: EACCES: permission denied, mkdir '/root/nope'"
#   at Object.mkdirSync (node:fs:1379:3)
#   at ...12 lines of stack trace...
# Now: clean "Cannot create output directory" error box

Stack

7/8 in the HyperFrames new-user bug fixes stack.

🤖 Generated with Claude Code

[miguel-heygen]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• fix(engine,cli): download headless-shell instead of using system Chrome for local renders #131
• fix(cli): improve error message for zero-duration composition renders #129
• fix(cli): catch output directory creation errors in render #130 👈 (View in Graphite)
• fix(cli): distinguish info vs warning severity in lint output #127
• fix(core): separate info count from warning count in linter results #126
• fix(cli): respect --json flag on lint error paths #125
• fix(cli): suppress ANSI escape codes in non-TTY progress output #124
• fix(cli): include all 9 templates in build output #123
• fix(cli): read actual data-width/data-height in info command #122
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[miguel-heygen]

errorBox parameter semantics are swapped

The errorBox signature is errorBox(title, hint?, suggestion?) where hint is rendered dimmed (informational) and suggestion is rendered accented (actionable command). Every other call site in this file follows that convention.

The current call passes the directory path as hint and the raw OS error as suggestion, which means the error message (e.g. "EACCES: permission denied") gets styled as if it were an actionable command.

Suggest:

errorBox(
  "Cannot create output directory",
  `${dirname(outputPath)}: ${message}`,
  "Check that you have write permission or specify a different path with --output.",
);

Also minor: `${dirname(outputPath)}` is equivalent to just dirname(outputPath) since it already returns a string — the template literal wrapping is unnecessary.

[miguel-heygen]

Addressed: fixed errorBox parameter order — error message now in hint slot, actionable suggestion ("Check write permission or use --output") in suggestion slot. Removed unnecessary template literal.

[miguel-heygen]

Consolidated into fix/render-improvements.