Add deterministic Java compile smoke test and PR CI check

[Nullkernel]

Motivation

• Provide a fast deterministic smoke test that compiles repository Java examples to catch broken files early.
• Avoid noisy whole-repo compile failures caused by default-package / filename collisions by compiling files in isolation.
• Run the smoke test automatically on pull requests via CI to prevent regressions.

Description

• Add scripts/compile_smoke.sh which scans Searching-algorithms/, Sorting-algorithms/, and Data-Structures/, sorts file paths for deterministic ordering, copies each file into an isolated temporary work directory (renaming to the declared public class/interface/enum name when present), compiles each file into a separate output folder, and emits [PASS] / [FAIL] per file while returning non-zero on any failures.
• Update README.md to document running the smoke test (./scripts/compile_smoke.sh) and describe its behavior (target directories, deterministic sorting, isolated outputs, and pass/fail semantics).
• Add a GitHub Actions workflow at .github/workflows/compile-smoke.yml that sets up Java 17 and runs ./scripts/compile_smoke.sh on pull_request and via workflow_dispatch.

Testing

• Ran the smoke test locally with ./scripts/compile_smoke.sh, iterated on the script to handle files whose public class name did not match their filename, and verified the final run printed Java compile smoke test passed. (all targeted Java files compiled in isolation).
• Created the CI workflow file .github/workflows/compile-smoke.yml so the same smoke test will run automatically on incoming pull requests (workflow creation not executed here).

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Codex Task