bregctl internal simplification candidates from the 0.28.0 review

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

None of these blocks a release; they are the places where the code is larger than the behavior it delivers:
- `bregctl init --from` wizard (`src/init_from_model/wizard.rs`, about 930 lines) refuses without a TTY; a commented selection template plus `--selection FILE` covers the same ground.
- `bregctl examples run` carries about 340 lines of attempt and resume bookkeeping behind five flags (`src/dev/examples.rs`).
- `src/dev/examples.rs:93-116` step grammar duplicates `crates/registry-breg/src/fixtures.rs:199-223`; share one definition.
- Standalone versus parent-workspace editor schema copies in `crates/registry-evidencectl/src/tooling_editor.rs:371-389`.
- The PublicSchema snapshot embeds 2.9 MB via `include_str!` with one starter using about 5% of it (`crates/registry-linkml/src/publicschema.rs`).
- `rhai_planner.rs:284-286` and `action_handler.rs:493-495` repeat the same Rhai error classification; fold into one helper.
- `crates/registry-breg/src/mutation/action.rs` (2,262 lines) also owns Evidence retention insert and erase (2090-2147); split them out.
- `crates/registry-bregctl/src/lib.rs` is 11,673 lines; split by command family.

Take them one at a time, each as its own PR with tests.

Choose one candidate rather than treating the list as a single change. Start with the named Rust file and its surrounding tests, then compare the referenced duplicate or oversized section. Done means one focused PR that preserves behavior, removes the selected duplication or split concern, and includes tests.

Written by the indexing model from the issue text.