test: add comprehensive unit tests for Template::Stash

[toddr-bot]

What

142 unit tests for Template::Stash, the core variable resolution engine.

Why

Existing stash_clone.t covers only clone/declone/define_vmethod/undefined (32 tests). The main stash.t is an integration test using Template::Test. The core get()/set()/_dotop()/_assign() methods had zero direct unit coverage.

How

Direct method calls with Test::More, exercising every public and internal method:

• Constructor — hash ref, flat list, empty, _PARENT override protection
• get/set — simple keys, compound array idents, dotted strings, intermediate hash creation, default mode, private member rejection, code ref invocation
• dotop — hash/array/object/scalar roots, vmethods, hash & array slices, code refs at indices, lvalue mode, blessed-hash fallback, method error propagation, multiple return folding, debug mode
• _assign — hash/array/object assignment, default mode, private rejection
• getref — simple & compound idents, mutation tracking
• update — regular keys, import (hash & non-hash)
• undefined — strict mode exceptions, .defined bypass (GH Can't use TABLE plugin with STRICT mode [rt.cpan.org #104569] #170), _reconstruct_ident
• PRIVATE — default pattern, custom regex, disabled

Testing

perl -Ilib t/unit-stash.t    # 142 tests pass
make test                     # full suite passes

🤖 Generated with Claude Code

---

Quality Report

Changes: 1 file changed, 888 insertions(+)

Code scan: 1 issue(s) found

• t/unit-stash.t:0 — 888 lines added

Tests: passed (OK)

Branch hygiene: clean

Generated by Kōan post-mission quality pipeline