CLI consistency batch across bregctl and evidencectl

Found in the 0.28.0 pre-release review (2026-09-08). Line references are as of main after #926.

Inconsistencies on already-released flags, to be fixed together in one deliberate breaking release rather than piecemeal (the unreleased ones were fixed before 0.28.0):
- Positional `[PROJECT]` with a default exists only on the four newest bregctl commands; older commands still take `--project`. Adopt positional everywhere and keep `--project` as a hidden alias for one release.
- `evidencectl` uses `--project` throughout; align with the bregctl grammar.
- Six spellings for preview versus commit across the two binaries; pick one (`--apply`, preview by default) and alias the rest.
- `--access-profile` carries opposite meanings on two commands.
- Three spellings for field flags.
- "starter" means four things: `init` starter, `examples` starter, PublicSchema starter, and the evidence starter directories. Pick one vocabulary.

Each change needs the api-stability rule applied (minor bump) and a BREAKING changelog line.

Start by inventorying the command definitions and flag handling in the bregctl and evidencectl entry points. Apply the api-stability rule while resolving the project, preview/commit, access-profile, field, and starter naming inconsistencies. Done means the agreed grammar is consistent across both binaries, aliases are retained as specified, and each change has a minor bump and BREAKING changelog line.

Written by the indexing model from the issue text.