fix: restore post-Joni core behavior

[fglock]

Summary

• restore Perl list snapshot semantics when map, grep, all, or any mutates its source
• return undef/EBADF for -t on descriptorless scalar handles
• fetch tied regex interpolation once per interpolation
• unwind dynamic locals, provisional captures, and $^R when a Joni callback throws
• update the Phase 36 plan with the remaining callback-transaction and scope blockers

The new Joni commits already recover op/index.t and op/index_thr.t. This PR recovers the other reported regressions without changing existing tests.

Regression results

Test	Regressed	This branch
op/array.t	0/0 timeout	182/199
op/stat_errors.t	634/638	638/638
op/tie_fetch_count.t	213/343	215/343
op/index.t	414/415	415/415
op/index_thr.t	414/415	415/415

Validation

• make — passed
• new unit tests under system Perl — 6/6
• new unit tests on JVM and interpreter backends — passed
• focused callback/dynamic-pattern tests on JVM and interpreter — passed
• make test-threads-regex — JVM 48/48 and interpreter 48/48; zero failures, errors, timeouts, or incomplete files

Remaining Phase 36 work

rxcode.t is currently 39/42 and reg_eval_scope.t is 22/49. The next implementation slice is matcher-owned mutation checkpoints for writes on abandoned backtracking paths, followed by callback pragma/caller/control-flow isolation. These are recorded in dev/design/phase36-regex-parity.md.