Bun parity: port mock functions and Jest spy matcher matrices

Scope

Port the unchanged upstream js/bun/test/mock-fn.test.js and js/bun/test/spyMatchers.test.ts suites to the Home bootstrap runner without TODO rewriting.

This tranche covers:

• Jest-compatible mock function prototype, metadata, state replacement, call contexts, instances, invocation ordering, one-shot implementations, and withImplementation restoration
• non-function jest.fn(value) return-value shorthand
• idempotent function/data-property spying, descriptor restoration, and indexed property keys
• incomplete recursive result tracking and return/call matcher semantics
• positive and negated objectContaining support in nested matcher equality
• permanent exact-count corpus regressions

Validation

• mock-fn.test.js: 54 passed, 0 failed, 0 unsupported, 0 todo
• spyMatchers.test.ts: 145 passed, 0 failed, 0 unsupported, 5 upstream-declared todo
• neighboring mock/expect matrix: 37 passed, 0 failed, 0 unsupported, 0 todo
• both activated fixtures are byte-identical to ~/Code/bun
• full ./pantry/.bin/zig build test -Dfilter=home_test --summary failures gate passes

Tracked under #66.

Completed in ebe5f0127.

The unchanged upstream matrices now run natively in Home:

• mock-fn.test.js: 54/54, 0 failed, 0 unsupported, 0 todo
• spyMatchers.test.ts: 145/145, 0 failed, 0 unsupported, 5 upstream-declared todo preserved
• neighboring mock/expect regressions: 37/37, 0 failed, 0 unsupported, 0 todo

Both activated fixtures are byte-identical to ~/Code/bun, permanent exact-count regressions are included, and the full home_test gate passes with zero failures.