bug(rewind): preserve literal markup when draft provenance is ambiguous #930

Expected behavior

Provider-authored wrappers require provenance. Preserve ambiguous user text rather than silently switching mode or stripping content.

Source finding and impact

claudeDraft searches decoded text for bash-input and command-name tags and strips recognized context tags without provenance. A literal user example containing those tags can be reinterpreted as execution mode or have surrounding text removed. The helper-level conditional path is source-confirmed; native-decoder reachability still needs a fixture.

Evidence and environment

Inspected source at 552914f5610518458f944fa1bdaf63f243685bd1 on 2026-09-12 in the local macOS workspace. This finding has not yet been reproduced through a running application or the package integration suite.

• src/main/providerSwitch/transcriptEngine.ts

Regression and acceptance

Pass literal markup examples through real Claude decoding and rewind draft reconstruction; distinguish genuine provider wrappers from user-authored examples. If native encoding proves an envelope unreachable, record that evidence and narrow the issue instead of adding a redundant test.

The resolving PR must protect the observable contract and document any remaining uncertainty. This planning pass makes no runtime changes.

Refs #918; planning finding F17.