feat: add actionable structured failure diagnostics

[cpendery (cpendery)]

Summary

• add a versioned FailureDetails envelope to core errors and carry it through CLI JSON, N-API, PyO3, JavaScript, and Python
• trace locator stages, effective occurrence, candidate counts, anchor/selection failures, style mismatches, and distinct polling outcomes
• retain bounded recent screen and operation history with pinned terminal, process, backend, profile, and timing evidence
• write collision-safe failure artifacts containing failure.json, deterministic report.md, pinned terminal text/SVG, and an optional immutable automatic-recording prefix
• add CLI artifact/context flags, configurable screen-history retention, and an explicit daemon protocol revision
• preserve human error messages and compatibility terminal fields while moving location() failures into the core

Failure artifact

Bundle mode writes:

failure-<timestamp>-p<pid>-<sequence>/
  failure.json
  report.md
  current.txt
  current.svg
  session.cast

failure.json is committed last and records file status, hashes, omissions, truncation, sensitivity, and capture errors. Recording copies are worker-snapshotted immutable prefixes; if output advances after the pinned failure observation, the cast is omitted instead of pairing mismatched evidence.

Compatibility and privacy

• existing error classes, messages, exit codes, and Terminal content: output remain available
• JavaScript retains the legacy newline native-error parser; Python retains message-only behavior for older native modules
• reused sessions keep their original history retention while each client/command can choose its own artifact policy
• artifacts can contain terminal output, titles, locator/assertion operands, snapshot evidence, diagnostic context, and recordings; recording inclusion is explicit
• TuiTestError is now non-exhaustive and exposes boxed diagnostic/artifact payloads to keep Result sizes bounded

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo clippy -p tui-test-rs --all-targets --no-default-features -- -D warnings
• cargo test --workspace -- --test-threads=1
• Python: 117 tests passed with the rebuilt worktree extension
• python bindings/python/scripts/generate_stubs.py --check
• JavaScript TypeScript compilation passed
• focused JavaScript native/options suites: 31 tests passed
• new N-API Rust code passed workspace check, clippy, and tests

The full npm run test:node path was not run because rebuilding the .node addon is blocked on this Windows machine by the existing Ghostty/Zig linking failure; focused JavaScript tests used the existing addon for mocked runtime behavior while the changed native Rust code was validated through Cargo.