feat(init): add shell completion installation step to mgw:init

[snipcodeit]

Summary

• Adds install_completions step to mgw:init that detects the user's current shell (bash/zsh/fish) and offers to copy the appropriate completion script from the bundled completions/ directory
• Step is opt-in by default in interactive mode (prompts [Y/n]) and skips gracefully in non-interactive/CI contexts, printing a manual install hint instead
• Completion install is idempotent — safe to re-run; overwrites existing file at target
• Init report updated with a Shell completions status line showing installed (bash|zsh|fish), skipped, or not available

Closes #124

Milestone Context

• Milestone: v4 — Interactive CLI & TUI
• Phase: 29 — Shell Completions and Config Wizard
• Issue: 8 of 9 in milestone

Changes

commands/init.md

• Updated description frontmatter to reflect completion install capability
• Added install_completions step (between ensure_labels and report) covering: package dir resolution, shell detection, per-shell target path mapping, interactive prompt with default-yes, non-interactive fallback hint, and activation instructions
• Updated report step to include Shell completions status line
• Added three new success_criteria entries for the completion install behaviour

Test Plan

• Run mgw:init in a new repo with mgw installed globally — verify prompt appears for detected shell
• Answer n — verify report shows Shell completions: skipped
• Answer y (or Enter) — verify file copied to correct target dir and activation hint printed
• Run again — verify idempotent (no error, overwrites existing)
• Run in non-interactive context (e.g. mgw:init < /dev/null) — verify prompt is skipped and manual install hint is shown
• Run without mgw globally installed — verify step is skipped silently and report shows not available

[snipcodeit]

Review: PR #168 — shell completion installation step in mgw:init

The UX design is good — opt-in prompt with sensible defaults, idempotent re-run, graceful skip in CI. Two issues need addressing.

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🔴 require.resolve("mgw/package.json") fails in development/local installs

The step uses:

MGW_PKG_DIR=$(node -e "require.resolve('mgw/package.json')" 2>/dev/null | xargs dirname)

require.resolve("mgw/package.json") works when mgw is installed as a named global package. But during local development (node bin/mgw.cjs or node dist/bin/mgw.cjs from the repo), the package name mgw may not be resolvable this way. The resolved path might point to a node_modules cache, not the local completions/ directory.

A more robust approach uses __dirname relative to the running script:

# In the context of bin/mgw.cjs (resolved to dist/bin/mgw.cjs at runtime):
MGW_PKG_DIR=$(node -e "console.log(require('path').resolve(__dirname, '..', '..'))") 
# Or for the installed case: navigate from dist/bin/ up to package root

Since the executor runs this as pseudocode inside a Claude session, the actual resolution should use the same getCommandsDir() path resolution pattern already used elsewhere in bin/mgw.cjs.

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🔴 Merge conflict with PR #169

Both this PR and PR #169 modify commands/init.md — specifically both add new <step> blocks and update the <report> section. They will conflict when merged sequentially. The two steps need to be reconciled:

• This PR adds: install_completions step + completion status line in report
• PR #169 adds: run_config_wizard step + config.json status line in report

Both PRs should coordinate on merge order. Recommend merging one, then rebasing the other on top and resolving the conflict. Add a note in both PR descriptions referencing this dependency.

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🟡 zsh ~/.zsh/completions/ is not in default $fpath

The target path ~/.zsh/completions/ is not in the default zsh $fpath. Users must also add:

fpath=(~/.zsh/completions $fpath)
autoload -Uz compinit
compinit

to their ~/.zshrc. The step currently mentions this only as a comment ("or add to ~/.zshrc if not already present") but does not make it clear that without this step, completions will not load at all.

Recommend showing this as a required follow-up action (not a comment) in the activation instructions printed after install.

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✅ Good points

• Default-yes prompt [Y/n] is the right UX for completion install
• Non-interactive fallback prints manual install hint — correct for CI
• Idempotent overwrite behavior is correct
• Per-shell target directory mapping is accurate for bash and fish
• Graceful skip when completions dir not found