Remove the OpenHuman framing from core (#18 §C4)

Deletes `default_openhuman_dir()` and its one caller,
`MemoryClient::new_local()`.

`new_local` is the constructor that produced openhuman#5570: it resolved
`~/.openhuman/workspace` from the home directory and never consulted the
host's workspace scoping, so on any scoped host the write landed in a
store nothing else reads -- it failed by succeeding. openhuman#5575
removed the last caller; the reviewer there noted no lint on the host
side can hold this line (a scanner needle for a dead function fails the
liveness check), so the deletion has to happen here.

`default_openhuman_dir` existed for `new_local` alone. With it gone,
core no longer knows the host's directory layout at all: every
construction path takes an explicit workspace directory.

What deliberately stays:

- `global::init_default()` -- `#[cfg(test)]`, and its doc already warns
  it must never run in production.
- The `"openhuman"` provider slug in the embedder resolution ladder --
  host config vocabulary, not directory framing; removing it breaks
  existing configs for no containment gain.
- `OPENHUMAN_OLLAMA_BASE_URL` in `TestEmbeddingHost` -- `#[cfg(test)]`.
- Test fixture prose mentioning OpenHuman.

`dirs` stays a normal dependency: `engine/persona.rs` still resolves the
home directory for persona files.

cargo test -p tinymemory-core: 804 passed, 0 failed
cargo clippy -p tinymemory-core --all-targets: clean
cargo fmt --all -- --check: clean

Author: YellowSnnowmann

core/src/lib.rs

@@ -79,22 +79,6 @@ pub use tinymemory_api::host::{
     DEFAULT_MEMORY_SYNC_INTERVAL_SECS,
 };
 
-/// The default OpenHuman root directory, `~/.openhuman`.
-///
-/// The host resolves this through `config::default_root_openhuman_dir`, which
-/// this crate cannot see. Reproduced here rather than added to the config seam
-/// because the two callers only need it as a last-resort fallback when no
-/// workspace was supplied.
-///
-/// # Errors
-///
-/// Returns `Err` when the home directory cannot be determined.
-pub fn default_openhuman_dir() -> Result<std::path::PathBuf, String> {
-    dirs::home_dir()
-        .ok_or_else(|| "Could not find home directory".to_string())
-        .map(|home| home.join(".openhuman"))
-}
-
 pub use ingestion::{
     ExtractedEntity, ExtractedRelation, ExtractionMode, IngestionJob, IngestionQueue,
     IngestionState, IngestionStatusSnapshot, MemoryIngestionConfig, MemoryIngestionRequest,

core/src/store/client.rs

@@ -128,19 +128,6 @@ impl MemoryClient {
         }
     }
 
-    /// Create a new local memory client using the default `.openhuman` directory.
-    ///
-    /// # Errors
-    ///
-    /// Returns an error string if the home directory cannot be resolved or if
-    /// initialization fails.
-    pub fn new_local() -> Result<Self, String> {
-        let workspace_dir = crate::default_openhuman_dir()
-            .map_err(|e| e.to_string())?
-            .join("workspace");
-        Self::from_workspace_dir(workspace_dir)
-    }
-
     /// Create a new memory client from a specific workspace directory.
     ///
     /// # Arguments