Prevent cross-worktree session bleed during managed session resume/load

ROADMAP #41 was still leaving a phantom-completion class open: managed
sessions could be resumed from the wrong workspace, and the CLI/runtime
paths were split between partially isolated storage and older helper
flows. This squashes the verified team work into one deliverable that
routes managed session operations through the per-worktree SessionStore,
rejects workspace mismatches explicitly, extends lane-event taxonomy for
workspace mismatch reporting, and updates the affected CLI regression
fixtures/docs so the new contract is enforced without losing same-
workspace legacy coverage.

Constraint: Keep same-workspace legacy flat sessions readable while blocking cross-worktree misuse
Constraint: No new dependencies; stay within the ROADMAP #41 changed-file scope
Rejected: Leave team auto-checkpoint history as final branch state | noisy/non-lore history for a single roadmap fix
Confidence: high
Scope-risk: moderate
Reversibility: clean
Directive: Preserve workspace_root validation on future resume/load helpers; do not reintroduce path-only fallback without equivalent mismatch checks
Tested: cargo test -p runtime session_control -- --nocapture; cargo test -p rusty-claude-cli resume -- --nocapture; cargo test -p rusty-claude-cli --test cli_flags_and_config_defaults; cargo test -p rusty-claude-cli --test output_format_contract; cargo test -p rusty-claude-cli --test resume_slash_commands; cargo test --workspace --exclude compat-harness; cargo check --workspace --all-targets; git diff --check
Not-tested: cargo clippy --workspace --all-targets -- -D warnings (pre-existing failures in unchanged rust/crates/rusty-claude-cli/build.rs)
Related: ROADMAP #41

ROADMAP.md

@@ -344,7 +344,7 @@ Priority order: P0 = blocks CI/green state, P1 = blocks integration wiring, P2 =
     - Forks inherit the parent's workspace root by default; an explicit re-bind is required to move a session to a new worktree, and that re-bind is itself recorded as a structured event so the orchestrator can audit cross-worktree handoffs.
     - Surface a `branch.workspace_mismatch` lane event so clawhip stops counting wrong-CWD writes as lane completions.
 
-    **Status.** A `workspace_root` field has been added to `Session` in `rust/crates/runtime/src/session.rs` (with builder, accessor, JSON + JSONL round-trip, fork inheritance, and given/when/then test coverage in `persists_workspace_root_round_trip_and_forks_inherit_it`). The CWD validation, the namespaced on-disk path, and the `branch.workspace_mismatch` lane event are still outstanding and tracked under this item.
+    **Status.** Done. Managed-session creation/list/latest/load/fork now route through the per-worktree `SessionStore` namespace in runtime + CLI paths, session loads/resumes reject wrong-workspace access with typed `SessionControlError::WorkspaceMismatch` details, `branch.workspace_mismatch` / `workspace_mismatch` are available on the lane-event surface, and same-workspace legacy flat sessions remain readable while mismatched legacy access is blocked. Focused runtime/CLI/tools coverage for the isolation path is green, and `cargo test --workspace --exclude compat-harness` passes. `cargo clippy --workspace --all-targets -- -D warnings` still fails on pre-existing lints in unchanged `rust/crates/rusty-claude-cli/build.rs`, so that lint cleanup remains outside this roadmap item.
 
 ## Deployment Architecture Gap (filed from dogfood 2026-04-08)