docs: align root tsfile-cli skill with current CLI

[ColinLeeo]

The root tsfile-cli skill still recommends the nonexistent sample command, removed output formats and flags, comma-separated projections, and outdated metadata fields. Update it against the current CLI help and implementation so agents use supported commands and interpret their results correctly.

Document sketch and export, explicit object scope, repeated -m options, current TAG predicates, output defaults and fields, CSV input NULL handling, and exit status. Keep the root skill self-contained and direct agents to runtime command help for the installed binary. Addresses TsFile-164.

Validation:

• Skill Creator's quick_validate.py passed.
• Executed the documented shell workflow covering all 10 CLI commands against the current mainline CLI; verified exported CSV values and physical layout output.
• Verified that a multi-object file requires scope for head, and that multi-table CSV export produces both numbered files and a complete manifest.
• git diff --check passed.