fix(completion): hide internal commands and suppress fish debug logs

[jeet-dekivadia]

Summary

• filter hidden commands from shell completion when no argument has been typed yet
• discard stderr from fish's internal completion probe instead of appending it to /tmp/fish-debug.log
• add focused regressions for the empty-input filter and embedded fish script

Why

The non-empty completion path already skips child.Hidden, but the initial empty-input branch did not. An initial tab press could therefore expose internal commands such as __complete, @completion, and @manpages.

The fish completion script also appended diagnostics from every tab-completion invocation to a fixed temporary file. Bash already suppresses the same internal probe's stderr. Applying the same behavior in fish avoids an unbounded cross-session debug log during normal CLI use.

Validation

• git diff --check
• go test ./internal/autocomplete -count=1

Remote Linux validation

• git diff --check
• ./scripts/bootstrap
• ./scripts/lint
• ./scripts/test

[jeet-dekivadia]

Small follow-up for review context. This patch is limited to completion behavior: hidden commands stay hidden at the shell-completion boundary, and the fish probe no longer writes debug noise to /tmp/fish-debug.log. The regressions cover both the hidden-command filtering and the fish script stderr behavior without touching command execution itself.

[markstuart-oai]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-06T01:30:06.247020Z	d23a9b6	Manual request
🔒 Security Review	✅ Completed 2026-09-06T01:31:21.465844Z	d23a9b6	Manual request

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Swish!

Reviewed commit: d23a9b6599

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Security review completed. No security issues were found in this pull request.

Reviewed commit: d23a9b6599

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[saioai]

please resolve the conflicts against main and keep the remaining hidden-command fix. the fish logging change already shipped, so please preserve the newer completion code and tests.