fix(#829): guard prefixed runtime variable launches

docs/architecture/mutator-class-gate.md

@@ -39,9 +39,17 @@ The executable submits the runtime's actual tool name to `authorize_tool`. Missi
 
 Every repository-owned Claude/Pi launch entry converges on `launch-runtime.py`, either directly or through `mosaic` → `execLeaseGatedRuntime`. PRDY init/update and QA remediation invoke the wrapper directly so their existing prompts, dangerous-permission behavior, working directory, and environment survive without skipping broker registration. The raw Claude `--dangerously-skip-permissions` primitive is owned only by `launch-runtime.py`; callers request semantic `--dangerous` mode, and the wrapper validates Claude before injecting the primitive. `@mosaicstack/coord` rewrites direct Claude commands to `mosaic claude` and rejects unknown custom Claude launchers.
 
-`check-runtime-launches.py` is the permanent completeness guard. It scans production shell, TypeScript/JavaScript, Python, and data launch definitions under `packages/`, `apps/`, `plugins/`, and `tools/`; direct literal, absolute-path, process-API, dynamic, command-substitution, `eval`, and variable-execution runtime launches fail. Shell comments are stripped with quote awareness, wrapper prefixes are tokenized with `shlex`, and only an invocation in command position with `--runtime` before the command separator is gated. A direct command always wins over an inert marker on the same line. Independently, the raw dangerous primitive anywhere outside the choke-point is RED.
+`check-runtime-launches.py` is the permanent completeness guard. It scans production shell, TypeScript/JavaScript, Python, and data launch definitions under `packages/`, `apps/`, `plugins/`, and `tools/`; direct literal, absolute-path, process-API, dynamic, command-substitution, `eval`, and variable-execution runtime launches fail. Shell comments are stripped with quote awareness, wrapper prefixes are tokenized with `shlex`, and only an invocation in command position with `--runtime` before the command separator is gated. Literal and tracked-variable command tokens use one terminal resolver after any nesting of `exec`, `command`, `nohup`, or `env` plus assignments. A direct command always wins over an inert marker on the same line. Independently, the raw dangerous primitive anywhere outside the choke-point is RED.
 
-Both checks are load-bearing: command-position analysis covers consequential launches that do not use dangerous mode, while primitive ownership cannot be fooled by a comment or marker string for dangerous mode. The guard is mandatory in `@mosaicstack/mosaic`'s test script, so root CI fails on a future bypass. Permanent regressions cover the original add-ungated effectiveness probe, comments, strings, assignments, heredocs, continuations, command chains, command substitution, `eval`, and variable execution; real-socket tests prove PRDY init/update and QA receive broker sessions and deny an unverified mutator.
+The command parser is a best-effort CI defense, not a complete shell interpreter. Alias/function redefinition, sourced commands, generated scripts, and encoded pipelines are intentionally residual rather than an invitation to chase an unbounded shell language. Two runtime controls backstop that residual surface: primitive ownership rejects a dangerous launch even when command identity is alias-indirected, and Claude's global `.*` `PreToolUse` hook invokes the broker gate for non-dangerous launches. Without `MOSAIC_LEASE_SESSION_ID`, representative read, mutator, and custom/MCP tools all fail closed with `GATE_UNAVAILABLE`. Hook absence or replacement remains in the documented T-C boundary.
+
+### Parser stopping criterion
+
+- **A — realistic parser matrix:** comments, inert strings/assignments, heredocs, continuations, chained commands, command substitution, `eval`, bare tracked variables, and quoted/unquoted tracked variables behind `exec`, `command`, `nohup`, or `env` are permanent RED regressions. Prefix-variable forms are covered in both multiline and same-line assignment shapes.
+- **B — residual backstops:** a dangerous alias-indirected launch is RED solely through primitive anchoring; a parser-missed non-dangerous alias launch is paired with an acceptance test proving the global all-tools hook denies every representative tool class as `GATE_UNAVAILABLE` without a lease.
+- **C — independent fresh review:** the parser class is considered complete only when reviewers find no new non-overlapping realistic evasion on the exact head. A and B are repository evidence; C is supplied by the fresh review round.
+
+All three layers are load-bearing and complementary. The guard is mandatory in `@mosaicstack/mosaic`'s test script, so root CI fails on a future realistic bypass. Real-socket tests separately prove PRDY init/update and QA receive broker sessions and deny an unverified mutator.
 
 The live inventory is emitted by: