Add explicit read-only mixed source8 CLI checking

docs/source-cli.md

@@ -64,3 +64,43 @@ are not a claim of interactive performance at the maximum project size.
 
 For the notation itself, start with [the text-first examples](../examples/text-first/README.md)
 and the [language contract](language.rst).
+
+
+## Read-only mixed source8 checking
+
+```sh
+arcadia check-mixed path/to/main.arcadia --json
+```
+
+Use `check-mixed` for source8 containing ordinary declarations and typed analysis
+(quantity kinds, units, calculations, properties, checks and cases). Every
+project, ordinary declaration, typed definition and scoped parameter must have
+an explicit UUID. This command does not migrate older headers, allocate UUIDs,
+format, preview edits or save. `--write` is a usage error. Existing `check`,
+`lint`, `stabilize` and `rename-alias` retain their ordinary-source behavior.
+
+The loader discovers actual includes with the source grammar and existing
+portable-path, regular-file, bounded-read and pending-journal checks. It captures
+original bytes, runs a bounded discovery syntax pass, then checks the complete
+borrowed bundle in a separate bounded verification pass. A discovery diagnostic
+prevents complete verification; the first mixed syntax/work failure stops
+further discovery parsing. Both passes derive limits from the same CLI policy;
+numeric work is bounded per pass, not once across the whole command. Logical
+producer limits are not a bound on all allocations or process memory.
+
+The format-1 JSON envelope uses operation `check-mixed`, status `checked` or
+`invalid` for completed source checking, and existing `rejected` for direct disk
+errors. `changes` is empty, `written` is false, `identities_to_stabilize` is zero,
+`migration` is null and `notes` is empty. Located diagnostics refer to original
+`input` bytes, with half-open UTF-8 byte spans and one-based Unicode-scalar
+line/column coordinates. Direct filesystem failures use the existing operation
+coordinate space. Engineering warnings permit exit 0; invalid source/semantics
+exit 1, usage exits 2, and disk/path/missing-file/pending-journal failures exit 3.
+Invalid UTF-8 discovery diagnostics retain the existing source-error exit 1.
+
+Human output goes to stderr and ends with `checked: mixed source8 check; no files
+changed` on success, after any warnings. No source bytes or directory entries
+are written, and pending saves are never recovered implicitly. Checking captured
+bytes does not establish an atomic multi-file snapshot against concurrent writers.
+This command provides validation only; mixed editing, adoption, GUI and history
+integration remain outside this interface.