Wires the mustache-completion source and mustache-linter into a CodeMirror 6
EditorView. Accepts kind (filters variables) and reducedContext (env-only for
connection URLs). singleLine prevents newlines for URL/header fields. Host
ref syncs when the parent replaces value (promotion prefill).
completion fires after {{ and narrows as the user types; apply() closes the
tag automatically. Linter raises an error on unclosed {{, a warning on
references that aren't in the allowed-variable set for the current condition
kind. Kind-specific allowed set comes from availableVariables().
Plan prose had spec §8 idealized leaves, but the backend NotificationContext
only emits a subset:
ROUTE_METRIC / EXCHANGE_MATCH → route.id + route.uri (uri added)
LOG_PATTERN → log.pattern + log.matchCount (renamed from log.logger/level/message)
app.slug / app.id → scoped to non-env kinds (removed from 'always')
exchange.link / alert.comparator / alert.window / app.displayName → removed (backend doesn't emit)
Without this alignment the Task 11 linter would (1) flag valid route.uri as
unknown, (2) suggest log.{logger,level,message} as valid paths that render
empty, and (3) flag app.slug on env-wide rules.
ALERT_VARIABLES mirrors the spec §8 context map. availableVariables(kind)
returns the kind-specific filter (always vars + kind vars). extractReferences
+ unknownReferences drive the inline amber linter. Backend NotificationContext
adds must land here too.
