docs: backfill CLI reference for reports and diagnostics commands

[gregggreg]

Gap

website/docs/cli-reference.md documented run, preview, task, and budget, but the reports and diagnostics commands had no coverage at all — no flag tables, and report and busfactor were missing from the command table entirely.

Scope

One file, one commit, branched from origin/main.

• Added a Reports and Diagnostics section documenting all 32 flags across status (2), logs (12), stats (2), report (9), busfactor (7), and doctor (0 — noted explicitly as taking no flags), each with names, shorthands, defaults, and accepted values.
• Added nightshift report and nightshift busfactor rows to the Core Commands table.
• Added --help/-h to the Global Flags table (cobra adds it to every command), and documented --version/-v separately as a root-only flag.

Verification

• Every flag name, shorthand, default, and enum value was read directly from the Flags().* registrations in cmd/nightshift/commands/{status,logs,stats,report,busfactor,doctor}.go — nothing inferred.
• --version/-v and --help/-h confirmed against a locally built binary. --version comes from Version: Version on rootCmd, not a persistent flag, so it is documented as root-only rather than global — nightshift status --version errors with unknown flag: --version.
• The busfactor positional-vs---path precedence is documented from busfactor.go (the flag wins; the positional is used only when the flag is empty; current directory otherwise).
• npm run build in website/ succeeds.

Identified but intentionally out of scope

• The Global Flags table lists --provider and --timeout as global, but they are per-command: --provider is on budget, budget snapshot, and budget history; --timeout is on run and daemon start. Neither is registered on the root command. Correcting this is a behavior-claim fix rather than a backfill, so it is left for a separate PR.
• config, init, install, uninstall, and completion are still absent from the Core Commands table.
• daemon, install, and uninstall have no flag documentation.
• preview, task, and budget still have example blocks without flag tables.

Nightshift-Task: docs-backfill
Nightshift-Ref: https://github.com/marcus/nightshift