feature/sem-entities-path-based

[MattCozendey]

sem entities now works via path, instead of being scoped to single files. this allows for repo-wide entity search across multiple files at once. The old calling shape remains the same, because "sem entities ./foo.ts" is, after all, also a path. By default, "sem entities" list all entities.

If only one file is found, no grouping happens.

[inspect-review]

inspect review

Triage: 20 entities analyzed | 0 critical, 0 high, 9 medium, 11 low
Verdict: standard_review

Findings (2)

1. [low] MCP tool API breaking change: EntitiesParams renamed from required file_path: String to optional path: Option<String>, so existing callers sending file_path will fail to deserialize (missing field) and break at runtime. Evidence: crates/sem-mcp/src/tools.rs changed to pub path: Option<String> and sem_entities now reads params.path.
2. [low] MCP directory mode silently skips unreadable/non-UTF8 files by ignoring read_to_string errors, returning partial/incomplete entity lists without signaling failure. Evidence: crates/sem-mcp/src/server.rs directory branch: if let Ok(content) = std::fs::read_to_string(&abs_path) { all_entities.extend(...) } (no else/error).

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Reviewed by inspect | Entity-level triage found 0 high-risk changes

[MattCozendey]

these risks are fair @rs545837 do you like the general direction of this PR? Should I fix those?