Release v2.0.0

SubX is now two crates. subx-cli 2.0.0 is the command-line tool you
already know — its behaviour, flags, configuration keys and JSON output
envelopes are unchanged from 1.9.1. The major version bump is a
library-surface change: the processing engine behind the CLI has been
extracted into subx-core 1.0.0, a standalone library so that programs
— like the SubX GUI — can embed subtitle matching, format conversion,
timeline synchronization and translation directly instead of shelling out.
Each crate is published to crates.io from its own repository's release tag
(subx-core from jim60105/subx-core,
subx-cli from this one), so the library can release on its own cadence for
all of its consumers. subx-core 1.0.0 is already published to crates.io.

Added

• The subx-core crate. The engine modules keep their familiar paths —
  what was subx_cli::core::matcher::MatchEngine is now
  subx_core::core::matcher::MatchEngine, with only the crate name swapped
  — so adopting the library directly is a crate-name substitution.
  Documentation for the published crate lives on docs.rs.
• A reporting seam for embedding applications. Every engine, factory,
  file manager, worker pool and AI provider client gained a with_reporter
  builder: an embedding program attaches a reporter and receives status
  messages, warnings, AI token usage and structured progress events
  (started / advanced per item / finished) instead of terminal output.
  Batch operations also honour cooperative cancellation through the
  reporter — an attached UI can stop a running batch cleanly, and a stopped
  batch reports which operations it completed. The CLI's own terminal
  behaviour is unchanged: the same messages on the same streams under the
  same JSON/quiet rules.
• Thread-safe format handling. The subtitle format types are now safe to
  share across threads, so embedding applications can drive format managers
  and converters from parallel code.
• A manual-offset timing helper usable without audio analysis.
  subx_core::core::sync::shift_subtitle_timing applies a timing shift to a
  subtitle without constructing the voice-activity-driven sync engine, so a
  caller that only re-offsets timings needs no audio stack.
• Output-location helpers (the archive-aware default output directory/path
  rules the convert and translate commands use) are public queries on
  collected input, and the component factory exposes the match configuration
  its loaded settings imply plus an engine builder that accepts a
  caller-modified copy of it.
• A shared test-support feature provides the project's test workspace
  builder and provider-mock helpers to downstream test suites; it is never
  enabled in a shipping dependency.

Changed

• The 2.0.0 major bump is a library-surface change. subx_cli's
  config / core / error / services modules are now re-exports of the
  subx-core crate; existing use subx_cli::... imports keep compiling
  unchanged, and the twelve configuration test macros and subx_cli::Result
  survive as re-exports. The subx-cli binary's command-line behaviour,
  flags, configuration keys and JSON envelopes are identical to 1.9.1.
• SubXError::exit_code and SubXError::user_friendly_message are now
  methods of a SubXErrorExt presentation trait
  (use subx_cli::cli::error_ext::SubXErrorExt;); the machine-readable
  category(), machine_code() and hint() stay on the error type itself.
  Error behaviour is unchanged.
• Building this repository from a git clone now requires the subx-core
  submodule: clone with --recurse-submodules, or run
  git submodule update --init --recursive afterwards.
• The batch progress bar now shows the parallel job's live status line
  (active / queued / completed counts) that was previously set but never
  rendered.
• subx-core's default branch is master (renamed from main before
  this release). .gitmodules records branch = master, both repositories'
  CI triggers and submodule-pointer ancestry assertions follow the new name,
  and the Dependabot referent comment and documentation are updated to match.

Fixed

• --output json no longer writes progress-bar frames to the terminal on
  the parallel match path — JSON mode's stdout stays machine-clean and the
  force-hide rule now covers every progress bar.

Removed

• Five unused direct dependencies were pruned (led by the notify subtree,
  seven packages in all), shrinking the resolved dependency graph that the
  security audit and every consumer's build carry. hound moved to
  test-only: it no longer links into the release binary.

Migration

• Users of the binary: none. subx-cli 2.0.0 behaves exactly like
  1.9.1.
• Library consumers: existing use subx_cli::... imports keep working
  through the compatibility re-exports. New code SHOULD depend on
  subx-core directly (published to crates.io as 1.0.0); the subx-cli
  library facade exists only as re-exports and its removal is a future
  major-version decision.

Documentation

• The reference documentation — architecture guide, command reference,
  configuration guide, machine-readable-output contract, AI provider guide —
  was refreshed for the two-crate layout, and the specification trees split
  with the crates: openspec/ specifies the CLI, subx-core/openspec/
  specifies the library.