feat: more clear definition and first base implementation for lua

Co-authored-by: Copilot <copilot@github.com>

specs/script.allium

@@ -8,6 +8,10 @@
 
 config {
     script_extension: String = "lua"
+    macro_timeout: Duration = 10.seconds
+    transform_max_toasts_per_script: Integer = 5
+    transform_max_toasts_total: Integer = 20
+    transform_max_toast_length: Integer = 300
 }
 
 enum ScriptStatus {
@@ -70,6 +74,44 @@ surface ScriptManagementSurface {
         RebuildScriptsFromFilesRequested(project)
 }
 
+surface ScriptRuntimeSurface {
+    facing _: ScriptRuntime
+
+    provides:
+        ValidateScript(source)
+        ExecuteScriptRequested(script, entrypoint, args, progress_sink)
+
+    @guarantee SandboxedExecution
+        -- User-authored Lua executes from a sandboxed runtime state.
+        -- Filesystem mutation, process control, package loading, and other
+        -- unrestricted host capabilities are unavailable unless explicitly
+        -- re-exposed by the host application.
+
+    @guarantee ExplicitHostCapabilities
+        -- Host-provided functions are exposed only through an explicit bds.*
+        -- capability table, never through ambient global access.
+
+    @guarantee MacroTimeout
+        -- Macro execution has a short timeout budget of config.macro_timeout.
+
+    @guarantee ManagedBatchExecution
+        -- Utility and transform scripts execute as managed jobs.
+        -- The contract does not define a fixed wall-clock limit for those
+        -- jobs because batch work can legitimately scale with project size.
+        -- Progress reporting, operator cancellation, and host orchestration
+        -- govern their lifecycle instead of a fixed timeout.
+
+    @guarantee ProgressFeedback
+        -- Long-running utility and transform scripts may emit progress updates
+        -- through explicit host APIs during execution.
+        -- Progress reporting is cooperative and flows through the supplied
+        -- progress sink rather than ambient global side effects.
+
+    @guarantee BatchCancellation
+        -- Managed utility and transform jobs can be cancelled by the host
+        -- operator boundary.
+}
+
 invariant UniqueScriptSlug {
     for a in Scripts:
         for b in Scripts:
@@ -92,7 +134,7 @@ rule CreateScript {
             title: title,
             kind: kind,
             content: content,
-            entrypoint: entrypoint ?? "render",
+            entrypoint: entrypoint ?? if kind = macro: "render" else: "main",
             status: draft,
             enabled: true,
             version: 1,
@@ -127,7 +169,7 @@ rule CreateAndPublishScript {
             title: title,
             kind: kind,
             content: null,
-            entrypoint: entrypoint ?? "render",
+            entrypoint: entrypoint ?? if kind = macro: "render" else: "main",
             status: published,
             enabled: true,
             version: 1,
@@ -158,11 +200,17 @@ rule ExecuteMacro {
     when: MacroExpansionRequested(script, template_context)
     requires: script.kind = macro
     requires: script.enabled = true
+    requires: script.entrypoint != ""
     -- Macro scripts are invoked during template rendering
     -- via [[slug param1=value1 param2=value2]] syntax in post content
-    -- They receive named parameters and the template context, return HTML
-    -- from a bounded Lua execution environment that exposes only approved
-    -- host capabilities
+    -- Unknown macro names are resolved against enabled macro scripts by slug.
+    -- They receive named parameters plus template_context.env fields that
+    -- include isPreview, mainLanguage, languagePrefix, hook, source.kind,
+    -- and translations.
+    -- They return HTML and run sequentially with config.macro_timeout per
+    -- invocation.
+    -- Macro failures degrade to empty output for that invocation and do not
+    -- abort rendering of the surrounding page.
     ensures: MacroOutputProduced(script, html_output)
 }
 
@@ -170,8 +218,11 @@ rule ExecuteUtility {
     when: RunUtilityRequested(script)
     requires: script.kind = utility
     requires: script.enabled = true
-    -- Runs on-demand from the UI in a bounded Lua execution environment,
-    -- produces stdout output
+    requires: script.entrypoint != ""
+    -- Utility scripts commonly perform long-running data manipulation work.
+    -- They are manually started by an operator action, run as managed jobs,
+    -- may issue host-backed API calls, may emit progress during execution,
+    -- and may be cancelled by the operator.
     ensures: UtilityOutputProduced(script, stdout)
 }
 
@@ -180,14 +231,35 @@ rule ExecuteTransform {
     -- Transform scripts run sequentially on blogmark deep link data
     -- Input: title, content, tags, categories, source url
     -- Each transform can modify the data before post creation.
-    -- Execution uses the same bounded Lua host API contract as other scripts.
+    -- Execution uses the same managed job host API contract as other batch
+    -- scripts and may report progress while mass-processing remote or local
+    -- content.
     let transforms = Scripts where kind = transform and enabled = true
-    for t in ordered_by(transforms, s => s.slug):
+    for t in ordered_by(transforms, s => s.updated_at, s => s.slug, s => s.id):
+        requires: t.entrypoint != ""
         ensures: TransformApplied(t, data)
 
+    @guarantee TransformTrigger
+        -- Transform scripts are triggered automatically by blogmark import.
+        -- Each script receives the current post candidate plus a context with
+        -- source='blogmark' and the originating URL.
+
+    @guarantee TransformPipelineContinuation
+        -- Transform errors are captured per script and do not roll back the
+        -- last valid post state produced by earlier transforms.
+        -- The pipeline continues with subsequent enabled transforms.
+
+    @guarantee TransformToastBudget
+        -- Transform scripts may emit toast feedback.
+        -- At most config.transform_max_toasts_per_script toasts are accepted
+        -- from any one transform, with a total budget of
+        -- config.transform_max_toasts_total across the pipeline.
+        -- Individual toast messages are truncated to
+        -- config.transform_max_toast_length characters.
+
     @guidance
         -- bds://new-post deep links from browser bookmarks
-        -- Max 5 toast notifications per script, 20 total
+        -- Ordering is deterministic: updated_at, then slug, then id
 }
 
 rule RebuildScriptsFromFiles {