feat(functions push): add --manifest path for non-SDK function types

The runner-based push path can only ship function types the Braintrust
SDK exposes builders for: tools, scorers, prompts, parameters. Topics-
pipeline types (facet, classifier) and inline-quickjs preprocessors
have no SDK builder, so AI-agent workflows that author lenses cannot
push them through `bt`.

`--manifest <path>` accepts a JSON file with three shapes — the
`/insert-functions` wire body `{"functions": [...]}`, a bare entry
array, or a single entry object. The body bypasses the SDK runner
and is posted directly to `/insert-functions` (the same endpoint
`bt topics config enable` uses to create classifier functions).

Reuses the runner path's preflight machinery: `parse_project_selector`
+ `add_selector_requirement` for project classification,
`validate_direct_project_ids` for direct-id verification,
`resolve_named_projects` (honors `--create-missing-projects`) +
`resolve_default_project_id` for project resolution, and
`validate_duplicate_slugs` for cross-specifier collision detection.
A pre-resolution dedup pass canonicalizes Fallback to its default
project name so duplicate slugs never trigger fresh-project creation
on the server.

Failure paths emit a manifest-aware `PushSummary` with `total_files: 1`
and `source_file: <manifest-path>` so JSON consumers see the right
context. Two-step parse distinguishes `ManifestInvalidJson` from
`ManifestSchemaInvalid`. Spinner is suppressed in `--json` mode to
keep stderr clean.

Mutually exclusive only with `--file` and the positional file paths
(the genuinely ambiguous overlap). Runner-specific options
(`--runner`, `--language`, etc.) are silently ignored on this path
so env-backed defaults don't block the command.

Closes #149.

Author: imen-kedir

src/functions/mod.rs

@@ -270,6 +270,15 @@ pub(crate) struct PushArgs {
     )]
     pub file_flag: Vec<PathBuf>,
 
+    /// Push raw JSON function definitions, skipping the SDK runner.
+    #[arg(
+        long = "manifest",
+        env = "BT_FUNCTIONS_PUSH_MANIFEST",
+        value_name = "PATH",
+        conflicts_with_all = ["files", "file_flag"]
+    )]
+    pub manifest: Option<PathBuf>,
+
     /// Behavior when a function with the same slug already exists.
     #[arg(
         long = "if-exists",
@@ -687,6 +696,35 @@ mod tests {
         assert!(msg.contains("--type"));
     }
 
+    #[test]
+    fn push_manifest_flag_parses() {
+        let _guard = test_lock();
+        let parsed =
+            parse(&["functions", "push", "--manifest", "fn.json"]).expect("parse push manifest");
+        let FunctionsCommands::Push(push) = parsed.command.expect("subcommand") else {
+            panic!("expected push command");
+        };
+        assert_eq!(
+            push.manifest,
+            Some(std::path::PathBuf::from("fn.json")),
+            "manifest path should be parsed"
+        );
+        assert!(push.files.is_empty());
+        assert!(push.file_flag.is_empty());
+    }
+
+    #[test]
+    fn push_manifest_conflicts_with_file_path() {
+        let _guard = test_lock();
+        let err = parse(&["functions", "push", "--manifest", "fn.json", "extra.ts"])
+            .expect_err("manifest+file path should conflict");
+        let msg = err.to_string();
+        assert!(
+            msg.contains("manifest") || msg.contains("--manifest") || msg.contains("conflict"),
+            "expected conflict-related error, got: {msg}"
+        );
+    }
+
     #[test]
     fn top_level_type_flag_still_parses_for_functions_namespace() {
         let _guard = test_lock();