Groovy: fix return-type/control-flow/nested-paren bugs in args regex

[squid-protocol]

Recovered from an abandoned background-agent worktree -- never committed at the time. Three real bugs in the "args" pattern:

• Lowercase primitive return types (void foo(), int add()) never matched since the return-type stepper required an uppercase first char. Added a primitive-keyword alternative alongside the existing capitalized-type branch, and allowed , so multi-param generic return types (Map<String, Integer> foo()) don't break after the first type param.
• The flat [^)]* param-list matcher truncated at the first inner ), breaking on one-level-nested calls in default values (int y = Math.max(3, 4)). Swapped for a bounded one-level-nesting form.
• No exclusion for control-flow keywords, so if (x) {, while (x) {, switch (x) {, for (i in ...) {, catch (Exception e) {, and synchronized(lock) { were all misread as method parameter blocks. Added the same negative-lookahead style func_start already uses.

Not yet verified against the golden-master corpus or opened as a PR -- needs the usual crucible_check.py pass before merging.

Description of Structural Changes

Visual Observatory Testing

• I tested the output JSON on GitGalaxy.io OR the Airgap Observatory.
• Flexbox constraints, HUD elements, and 3D rendering remain intact.

The Differential Scan Acknowledgement

• I understand that my PR will be subjected to a Full Differential Scan.
• I have provided the link to the specific repository this PR addresses so it can be tested alongside the 80-repo calibrated baseline.
• I believe these changes will measurably improve the engine's Accuracy, Speed, Utility, or Ethos without causing regressions.