v0.18.0 - Add System Requirements Specification (SYSRS) Domain

Added

• New sysrs (System Requirements Specification) domain: an aggregator
  document type that ties together existing gol/prb/qa/uc/req/
  rsk/dec/adr/vcr artifacts into one coherent, navigable
  specification via per-section, type-tagged cross-reference lists (e.g.
  ### Goals accepts only GOL bullets, ## Decisions accepts DEC or
  ADR, and the nine ## Requirements H3s plus six ## Other Characteristics H3s each accept only REQ) rather than duplicating
  their content. Dispatch-only from day one, with no update_sysrs/
  set_status_sysrs tools of its own — whole-body/line-range updates,
  status changes, classification changes, and deletions all go through
  the existing generic update/set_status/set_classification/
  delete tools (type="sysrs"). Ships 7 tools (create_sysrs,
  parse_sysrs, list_sysrs, get_sysrs, get_sysrs_example,
  get_sysrs_template, validate_sysrs), 3 resources
  (specmgr://sysrs/schema, specmgr://sysrs/example,
  specmgr://sysrs/template), and 2 prompts (create_sysrs,
  update_sysrs) (GitHub issue #32).

• New specmgr://config resource: reports, for all twelve document
  domains, the resolved absolute base directory and whether the domain's
  SPECMGR_*_DIR environment variable is explicitly set, so a client can
  self-diagnose a working-directory-relative base-directory
  misconfiguration. Only the twelve known env var names are ever read
  (never os.environ wholesale), so no unrelated secret is ever
  disclosed. The "Add to OpenCode" README example now shows two
  alternatives for pinning the resolved base directory — uv/uvx's
  --directory flag, or explicit SPECMGR_*_DIR environment variables in
  the MCP client config — and documents the previously-missing
  SPECMGR_FEAT_DIR variable (GitHub issue #51).

• create_uc/update_uc MCP prompts for the uc (Use Case) domain,
  mirroring the req domain's prompt pattern and including
  set_classification guidance (GitHub issue #57).

Fixed

• format_text()/format_markdown_document() (models/md/_markdown.py),
  and transitively every domain's parse_<d>/create_<d>/validate_<d>/
  update path plus the mdformat CLI command and MCP tool, now render a
  thematic break (---, ***, ___, or any other CommonMark-valid
  variant) as a literal --- instead of mdformat's hardcoded 70-character
  underscore line ("_" * 70, not otherwise configurable upstream — see
  hukkin/mdformat#69). Fixed by wiring the third-party
  mdformat-simple-breaks plugin (pinned exactly, ==0.1.0) into the
  shared mdformat.text(...) call via its mdformat.parser_extension
  entry point (GitHub issue #47).