skillscript-runtime v0.4.0

connectors.json loader + credential discipline (config plumbing).
First MCP-scripting-era release. Wires the per-host connector
configuration the ERD §3+§4 spec has called for since T2. Loads
connectors.json at runtime startup, parses + validates, resolves
${VAR} substitutions, and registers each declared instance into the
Registry. Closed-set class registry + two new tier-1 lint rules. Spec
at b3f6c5ed (Perry kickoff) + 58a9d3d3 (credential amendment) +
8f723b6a (final approval).

Split note: RemoteMcpConnector (the stdio-bridge class for remote
MCPs via mcp-remote etc.) deferred to v0.4.1. v0.4.0 ships the
mechanism — loader, validation, lint, discovery, credential discipline
— but the only class in the v0.4.0 closed set (CallbackMcpConnector)
isn't JSON-instantiable (it requires a dispatch function). v0.4.1
adds RemoteMcpConnector as the first real configurable class, plus
the YouTrack end-to-end proving test.

Added

• connectors.json loader. Reads from BootstrapOpts.connectorsConfigPath
  (caller-supplied path; bootstrap stays explicit, doesn't auto-discover).
  Missing file → graceful empty result. Malformed JSON / structural
  errors / unknown class / unset ${VAR} → clear startup errors via
  BootstrapResult.connectorConfigErrors. Permissive on unknown
  fields so v0.4.1 schema additions (allowed_tools, etc.) plug in
  without breaking compat.

• Credential resolution: two shapes. Matches Claude Desktop's
  mcp.json convention:

  • Literal: "AUTH_HEADER": "Bearer plnt-..." (in-file)
  • Env-var substitution: "AUTH_HEADER": "Bearer ${YOUTRACK_TOKEN}"
    (resolved from process.env at load time)

  Missing ${VAR} → clear error (not silent empty-string substitution).
  Both shapes work; deployments should prefer ${VAR} per the
  credential-discipline section.

• Closed-set class registry. v0.4.0 set: {CallbackMcpConnector}.
  Plugin-style runtime-arbitrary class loading deliberately out of
  scope (security surface, discoverability, API maturity). Unknown
  class in connectors.json → clear startup error listing the known
  set. The set grows via CHANGELOG-tracked runtime releases.

• unknown-connector tier-1 lint. Fires on $ name.tool ops
  where name isn't a wired connector. Includes the list of wired
  names in the diagnostic so cold authors can correct typos quickly.
  Silent when the caller doesn't know what's wired (no false positives).

• unknown-connector-class tier-1 lint (Perry's sibling addition,
  8f723b6a). Re-surfaces the loader's "unknown connector class"
  errors via the lint API for tooling that consumes lint as the
  primary diagnostic surface (compile_skill / lint_skill MCP).

• runtime_capabilities discovery extension. New include
  option: mcpConnectorClasses returns the closed-set class names.
  Cold authors introspect "what classes can I configure?" before
  writing class: "..." fields.

• Credential discipline (hard requirement). Perry's amendment
  promoted from footnote to ship requirement:

  • connectors.json added to repo root .gitignore (root-anchored
    so the scaffold's bundled placeholder stays tracked)
  • connectors.json.example shipped at repo root as the version-
    controlled template
  • README "Connector model" section documents both credential
    shapes + the gitignore default + the discipline rationale
  • Loader-time gitignore-detection warning deferred to v0.4.1

New module

• src/connectors/config.ts — loader + env substitution + closed-set
  class registry. ~190 LOC including docstrings. Public surface:
  loadConnectorsConfig({path, env?}), listKnownConnectorClasses(),
  resolveEnvSubstitution(value, env), KNOWN_CONNECTOR_CLASSES.

Implementation notes

• Narrow-core LOC ceiling 5750 → 6000. Net ~190 LOC from the new
  connectors/config.ts module plus ~50 for the two lint rules and
  the mcpConnectorNames LintContext field. Consistent with v0.3.0's
  200-LOC nudge for $append. History entry in loc-ceiling.mjs.

• BootstrapOpts.connectorsConfigPath is explicit (no auto-
  discovery from CWD). Embedders pass the path; the CLI's
  skillfile dashboard / skillfile serve / skillfile execute
  surfaces will auto-pass ${cwd()}/connectors.json in v0.4.1+ once
  RemoteMcpConnector makes the file practically useful. Until then,
  embedders opt in explicitly.

• Tests: 31 new in tests/v0.4.0.test.ts covering loader basics
  (missing file, malformed JSON, structural errors, unknown class),
  env substitution (literal pass-through, ${NAME} resolution,
  missing var error, multiple substitutions, lowercase-name ignore),
  closed-set registry (v0.4.0 set, no RemoteMcpConnector yet),
  bootstrap wiring (graceful missing, errors surface, no false adds),
  both lint rules (positive + negative + silent-when-undefined),
  runtime_capabilities surface, and credential discipline (gitignore +
  example + README content). 897/901 passing (3 long-skip browser
  dogfood).