Prevent long sessions from stalling and expose the requested internal command surface

The runtime now auto-compacts completed conversations once cumulative input usage
crosses a configurable threshold, preserving recent context while surfacing an
explicit user notice. The CLI also publishes the requested ant-only slash
commands through the shared commands crate and main dispatch, using meaningful
local implementations for commit/PR/issue/teleport/debug workflows.

Constraint: Reuse the existing Rust compaction pipeline instead of introducing a new summarization stack
Constraint: No new dependencies or broad command-framework rewrite
Rejected: Implement API-driven compaction inside ConversationRuntime now | too much new plumbing for this delivery
Rejected: Expose new commands as parse-only stubs | would not satisfy the requested command availability
Confidence: medium
Scope-risk: moderate
Reversibility: clean
Directive: If runtime later gains true API-backed compaction, preserve the TurnSummary auto-compaction metadata shape so CLI call sites stay stable
Tested: cargo test; cargo build --release; cargo fmt --all; git diff --check; LSP diagnostics directory check
Not-tested: Live Anthropic-backed specialist command flows; gh-authenticated PR/issue creation in a real repo

rust/crates/runtime/src/lib.rs

@@ -30,8 +30,8 @@ pub use config::{
     CLAUDE_CODE_SETTINGS_SCHEMA_NAME,
 };
 pub use conversation::{
-    ApiClient, ApiRequest, AssistantEvent, ConversationRuntime, RuntimeError, StaticToolExecutor,
-    ToolError, ToolExecutor, TurnSummary,
+    auto_compaction_threshold_from_env, ApiClient, ApiRequest, AssistantEvent, AutoCompactionEvent,
+    ConversationRuntime, RuntimeError, StaticToolExecutor, ToolError, ToolExecutor, TurnSummary,
 };
 pub use file_ops::{
     edit_file, glob_search, grep_search, read_file, write_file, EditFileOutput, GlobSearchOutput,