skillscript-runtime v0.7.0

Syntax revamp + pre-adoption clean break. Two grammar additions
(canonical ${VAR} substitution + function-call op shape), two new
runtime-intrinsic ops (file_read, file_write), one throwaway script
that mechanically rewrites every prior-version skill to the new
surface. Legacy forms ($(VAR), ~, >, @, !, ??, &) continue
to compile + run during the grace period; tier-1 lint promotion lands
in v0.8/v0.9. Per Perry's kickoff 50a83a88 + final consolidated framework
c48fca7e + approval 783a10a4.

Added (canonical surface)

• ${VAR} substitution canonical form. Replaces $(VAR) (legacy,
  still works during grace period). Field access ${VAR.field} +
  filter chain ${VAR|filter:"arg"|filter2} work identically. Closes
  the bash-command-substitution collision ($(date) runs date in
  bash; ${VAR} is bash variable-interpolation — same intuition path,
  no semantic ambiguity). The $$(VAR) shell-escape gains a parallel
  $${VAR} form.

• Function-call op grammar. verb(kwarg=value, ...) [-> BINDING].
  Closed runtime-intrinsic set: emit, ask, inline, execute_skill,
  shell, file_read, file_write. Paren-balanced parsing (nested
  parens in kwarg values handled), comma-separated kwargs, quote-aware.
  Unknown function-call names produce a parse error with remediation:
  "if this is an MCP tool, use $ tool args -> R shape instead."

• file_read(path=) -> CONTENT runtime op. Reads file contents
  via Node fs.readFile. Substitutes ${VAR} in the path. Optional
  (fallback: "...") trailer for missing-file handling. New
  runtime-intrinsic op for skills that pull data from local files for
  prompt-context injection or processing.

• file_write(path=, content=, approved="...") runtime op. Writes
  contents via Node fs.writeFile. Auto-creates parent directories
  (mkdir -p semantics). Substitutes ${VAR} in both path and content.
  The approved= kwarg is the v0.7.0 author-intent marker for mutation
  ops outside # Autonomous: true skills; lint enforcement broadens
  in v0.7.1.

• approved="reason" inline kwarg shape. Captured on every
  function-call AST node; uniform with the all-kwargs discipline.
  Required string value forces author intent (presence matters; value
  not parsed semantically). Replaces the (approved: "...") trailer
  syntax for function-call ops (legacy trailer still works on symbol-
  form ops).

Changed (substrate framing)

• local_model and memory_query removed as language keywords.
  Pre-v0.7.0: ~ and > ops dispatched to amp's amp_invoke_local_model
  and amp_query_memories MCP tools via hardcoded paths — amp-specific
  privilege baked into the language. v0.7.0: they become regular
  $ <connector> MCP dispatch resolved against connectors.json.
  Tradita wires llm + memory as connector names pointing at amp;
  external adopters wire whatever substrate they use. Language stops
  assuming amp is the substrate.

Architectural framework

Per the design conversation captured in thread 50a83a88 → c48fca7e:

• Skillscript is a compose-time prompt-construction language. Its
  job is to build the prompt-context the agent receives, with optional
  pre-dispatch optimizations baked in. Not a general execution
  environment.
• Two layers: compose (skillscript) + execute (agent at higher
  level with native Read/Write/Bash/MCP tools).
• Three delivery channels — embedded prompt (emit), memory
  handoff ($ memory_write), file handoff (file_write). All
  first-class.
• Three op classes — mutation statements ($set/$append),
  runtime-intrinsic function-calls, external MCP dispatch.

Migration + harness cleanup

One-shot Node script (scripts/migrate-v07.mjs, removed after use)
rewrote examples/ from legacy to canonical (9 files, 138 rewrites:
92 substitution-shape + 25 emit + 8 tilde + 7 shell + 5 memory + 1
ask). Markdown-aware, idempotent. No permanent CLI surface.

Pre-adoption harness cleanup. The wild-and-crazy harness corpus
(R1/R2/R3 cold-author fixtures from v0.2.9 production) — tests/skills/,
tests/fixtures/harness/, tests/harness-corpus.test.ts,
tests/skills-battery.test.ts — removed in this release. Pre-adoption
means no external users depend on backwards-compat regression coverage;
R4 will rebuild fresh fixtures against canonical v0.7.0 syntax. Test
count drops ~187 (harness-corpus 66 + skills-battery 121) but the
remaining 896 tests cover the parser/runtime/lint paths comprehensively,
and v0.7.0-brace-substitution + v0.7.0-function-call ship 30 new tests
specific to the canonical surface. Git history preserves the discarded
fixtures if any are ever wanted as legacy snapshots.

Deprecation grace period

Legacy syntax ($(VAR), ~, >, @, !, ??, &) continues to
compile + execute in v0.7.x — both forms work identically during the
grace window. Tier-2 deprecated-symbol-op lint (visibility nudge)
ships in a v0.7.x point release; tier-1 promotion (refuse-to-compile)
lands in v0.8 or v0.9 once adopter ecosystem confirms migration.

LOC ceiling

Narrow-core ceiling nudged 6800 → 7150 (current: 7078). ~280 LOC
across parser.ts (function-call grammar + REF_PATTERN const + paren-
balanced helpers) + runtime.ts (file_read/file_write + loose-bracket
condition regexes + $${ escape) + compile.ts (alternation substitute

• new op renderers) + lint.ts (4-capture extractVarRefs). Per the
  v0.5.0 lesson loc-vs-clarity: ceiling is a signal, not a budget.

Tests

30 new tests across 2 files (v0.7.0-brace-substitution.test.ts,
v0.7.0-function-call.test.ts). All 7 runtime-intrinsic function-call
ops covered + ${VAR} substitution in all positions (substitution body,
conditions, $set RHS, kwarg values) + file_read/file_write round-trip

• mkdir-p + fallback + mixed legacy-and-new in same skill. Net suite
  (after harness cleanup): 896 passing, 10 skipped, 1 env-gated
  (YouTrack token).