fix(require): preserve $@/$! across on_scope_end callbacks

[fglock]

Summary

When a use Foo; inside a module being loaded throws "Can't locate
Foo.pm in @inc", ModuleOperators.doFile's catch block stores that
message in $@. The finally block then calls
BHooksEndOfScope.endFileLoad, which fires the on_scope_end
callbacks registered for the file. Some of those callbacks (notably
namespace::autoclean's cleanup routine) internally use eval { ... }
blocks, which Perl resets $@ to "" on success — clobbering the
inner cause. By the time the outer require reads $@ it is empty,
only $! (ENOENT) is left, and the outer require falls into the
"file not found" branch and rebuilds an error message naming the
outer module.

This makes failures look very wrong. For example,
jcpan -t Text::WordCounter reports

Can't locate Text/WordCounter.pm in @INC (you may need to install
the Text::WordCounter module) (@INC entries checked: blib/lib …)

even though blib/lib/Text/WordCounter.pm exists; the real failure
is Can't locate Lingua/ZH/MMSEG.pm in @INC from a use inside
Text/WordCounter.pm.

Reproducer

# /tmp/MyWC.pm
package MyWC;
use namespace::autoclean;
use Moose;
use NotExistsBogus;
1;

$ jperl -I/tmp -e 'eval { require MyWC; }; print $@'
# before: Can't locate MyWC.pm in @INC ...   (misleading)
# after : Can't locate NotExistsBogus.pm in @INC ...  (correct)

Fix

BHooksEndOfScope.endFileLoad now saves $@/$! before invoking the
on_scope_end callback loop and restores them in a finally, so the
inner failure message survives.

Test plan

• make passes (all unit-test shards green)
• Reproducer above shows the corrected error message
• jcpan -t Text::WordCounter now reports the real underlying
  cause (Can't locate Lingua/ZH/MMSEG.pm in @INC) instead of a
  misleading "Text/WordCounter.pm" message
• Configuration.java regenerated by injectGitInfo is included

Generated with Devin

[fglock]

Update — phases 2 and 3 of dev/modules/text_wordcounter.md

This branch now carries three commits, each fixing a distinct
PerlOnJava parity bug surfaced by jcpan -t Text::WordCounter:

1. 4850e9a83 — preserve $@/$! across on_scope_end callbacks (original)

Stops misleading Can't locate <outer-module>.pm errors when an
inner use Foo; fails inside a module that uses
namespace::autoclean + Moose.

2. 88f63c8c9 — bundle no-op encoding.pm pragma

The deprecated encoding pragma (removed from core in 5.26+) is
still loaded by older CJK CPAN modules. PerlOnJava parses sources
as UTF-8 unconditionally, so a no-op stub that honours explicit
filehandle-layer arguments is sufficient. Includes a unit test.
Result: Lingua::ZH::MMSEG 3/3 tests pass.

3. cd93247e4 — $SIG{__DIE__|__WARN__} = 'DEFAULT'/'IGNORE'

Real Perl 5 treats those two literal strings in %SIG as reserved
("no handler" / "ignore"). PerlOnJava was invoking them as
subroutine names — when URI::Find::find does
local $SIG{__DIE__} = 'DEFAULT'; and URI.pm then does
eval "require URI::git", the failure dispatched through a
bogus &main::DEFAULT() and clobbered $@, making git://
and svn+ssh:// URIs undetectable.
Result: URI::Find 578/578 subtests pass.

4. 7819bbe00 — plan docs

dev/modules/text_wordcounter.md updated to reflect what shipped
here, including a corrected explanation of the URI::Find failure
(not a regex-parity bug after all) and a new Work item 5 covering
the remaining blocker:

• Loading Unicode::UCD from the shaded jar via the module-name
  form materialises only 3 of 44 subs, so
  Text::WordCounter::split_scripts dies with
  Undefined subroutine &Unicode::UCD::charinfo called. Loading
  the same file via an absolute path (or via do) materialises
  all 44 subs. Diagnosis is left for a follow-up PR.

Cumulative effect on jcpan -t Text::WordCounter

• Lingua::Stem::Snowball::No: PASS
• Lingua::Stem::Snowball::Se: PASS
• Lingua::Stem: PASS
• Lingua::ZH::MMSEG: PASS (was: FAIL)
• URI::Find: PASS 578/578 (was: FAIL 2/578)
• Text::WordCounter: still fails — blocked on Work item 5

Test plan

• make passes (all unit-test shards green)
• New encoding_pragma.t unit test passes (6/6 subtests)
• Lingua::ZH::MMSEG t/000-load.t, t/002-mmseg.t, t/003-fmm.t all pass
• URI::Find t/Find.t passes 578/578 (previously 576/578)
• Configuration.java regenerated by injectGitInfo is included