feat: advance Perl threads phases 25 through 30

[fglock]

Summary

• preserve magic regex captures, cleared weak references, CODE roots, constants, and lazy compiled-code identity across ithread snapshots
• improve shared JVM/interpreter scalar lvalue behavior, user Unicode-property coordination, thread API lifecycle/context/signals/stack metadata, and inherited internal pipes
• add general recursive-regex (?(DEFINE)) support, focused system-Perl-valid tests, a realistic dynamic map/reduce example, and updated design progress

Validation

• make after rebasing onto origin/master: PASS (all unit shards)
• system Perl: 9 new files / 56 assertions PASS
• new Perl tests: JVM and interpreter focused coverage
• pat_psycho_thr.t: 17/17 after previously terminating before TAP
• pat_rt_report_thr.t: no clone/compiled-ID exception; matches the direct 2478-pass count
• map/reduce example: system Perl, JVM, and interpreter PASS with identical output

Explicit follow-ups

• Phase 26 remains in progress for one interpreter lazy-lexical identity case and remaining direct substr.t assertions
• lexical re 'debug', pat_re_eval, and the remaining regexp_qr_embed surface are direct regex-language work, not thread-wrapper special cases
• detached platform-thread shutdown warnings/process retention and non-pipe resource classes remain follow-up lifecycle work

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