Refactor canonical edit intent ownership

[isty2e]

Summary

• require whole-file move changesets to carry canonical preview.move.{from,to} data
• reorganize apply/edit integration suites by behavior ownership without dropping discovered tests
• normalize edit and patch flag mode through one private edit-intent model while preserving their distinct lifecycles

Responsibility map

• changeset: owns canonical text-vs-move preview families and rejects missing, mixed, or legacy placeholder move previews at ingress
• cli::edit_intent: owns shared flag arguments, target selection, text-source resolution, and prepared intent normalization
• cli::edit: resolves an intent and builds a changeset without writing
• cli::patch: resolves the same intent and executes apply/dry-run behavior
• integration tests: split into content edits, file targets, file moves, request validation, transactions, filesystem/atomicity, structural moves, and related owners

Contract and compatibility

• move operations now require preview.move with matching from and to; empty text placeholders and missing move preview data fail at ingress with a regeneration diagnostic
• edit --identity and patch's hidden --identity/--anchor aliases are removed; --at is the canonical selector
• edit gains the same single-target flag capabilities as patch, but remains build-only
• patch remains the one-shot apply path; --dry-run remains non-mutating
• JSON and multi-file edit behavior are unchanged
• no external downstream consumer was available in the workspace; the two compatibility breaks above are intentional for the pre-1.0 CLI

Public graph and dependencies

• added no library-public API; the crate remains binary-only
• added private cli::edit_intent ownership and removed duplicate cli::patch::{flag,target,text} ownership
• caller paths shorten to EditIntentArgs -> PreparedEditIntent -> edit build | patch execute
• dependency direction remains one-way: edit/patch commands depend on edit-intent normalization; edit-intent does not depend on command execution

Lean decisions

• accepted: remove optional move-preview state, legacy placeholder normalization, duplicate flag parsers, and scenario-number test ownership
• rejected: reintroducing timing-sensitive rollback tests removed from current main
• rejected: merging edit and patch execution lifecycles, because build-only versus apply/dry-run is a real invariant
• rejected: a generic target/operation abstraction beyond the concrete shared intent model

Validation

• cargo test --locked --all-targets --quiet (2,038 tests passed)
• cargo clippy --locked --all-targets -- -D warnings
• cargo fmt --all -- --check
• cargo build --locked --release
• git diff --check origin/main...HEAD
• focused suites: changeset unit tests, apply (190), edit (124), patch (772), merge (4), and CLI surface (15)

Residual risk

• consumers that persist pre-change move changesets must regenerate them
• scripts using the former edit --identity flag or patch's hidden --identity/--anchor aliases must switch to --at