Fix basectl gh Project completion drift

[codeforester]

Problem

The Bash completion surface has drifted from the current basectl gh project command help.

Current examples:

• cli/bash/commands/basectl/subcommands/gh.sh documents basectl gh project configure --config <path> and --copy-fields-from <title>.
• cli/bash/commands/basectl/subcommands/gh.sh documents basectl gh project issue set-fields --config <path>.
• lib/shell/completions/basectl_completion.sh does not complete those options in the corresponding gh project branches.

Scope

• Refresh lib/shell/completions/basectl_completion.sh for the current basectl gh project option surface.
• Add or update focused completion coverage so the command help and completion stay aligned.
• Keep this PR limited to completion drift; do not refactor the completion engine.

Acceptance Criteria

• basectl gh project configure completes --config and --copy-fields-from.
• basectl gh project issue set-fields completes --config.
• Focused completion tests pass.
• Shell syntax and ShellCheck remain clean for the touched Bash files.

[codeforester]

Bash Review PR Train

Suggested implementation order:

1. Fix basectl gh Project completion drift #1487 - Fix the completion drift first. This is the smallest user-visible bug and gives the train a fast validation baseline.
2. Clear warning-level ShellCheck findings in non-test Bash code #1493 - Clear warning-level ShellCheck findings next so later PRs work from a cleaner shell-lint signal.
3. Expand reusable GitHub Bash helpers base-bash-libs#119 - Expand the reusable GitHub Bash helpers in the shared library before changing Base call sites.
4. Consume expanded GitHub Bash helpers in Base #1488 - Consume the expanded GitHub helpers in gh.sh and repo.sh after the shared helper release or sibling checkout is available.
5. Finish update-profile file-helper adoption #1492 - Finish update_profile.sh file-helper adoption while the shared-library context is fresh.
6. Reduce remaining setup_common Bash temp and diagnostic helper surface #1490 - Reduce the remaining setup_common.sh temp/diagnostic helper surface, keeping behavior stable.
7. Deduplicate first-mile install and bootstrap Bash helpers #1491 - Deduplicate first-mile bootstrap.sh and install.sh helper logic without adding runtime dependencies.
8. Move repo Project Intake workflow generation out of inline Bash #1489 - Move the generated Project Intake workflow out of inline repo.sh Bash last, because it has the broadest repo baseline and generated-output surface.

Notes:

• Do not split large Bash files mechanically.
• Keep Base product workflow in Base.
• Put reusable shell primitives in base-bash-libs only when they are proven by at least one Base call site and are free of Base product policy.