feat(ci): optimize workflow with path-based conditional job execution

[bug-ops]

Summary

Implements path-based conditional job execution to optimize CI pipeline performance.

Closes #11

Changes

• Path-based change detection: Added changes job using dorny/paths-filter@v3 to detect which files changed:

  • rust-core: Core Rust crate, Cargo.toml, Cargo.lock
  • python: Python bindings (includes core as dependency)
  • node: Node.js bindings (includes core as dependency)
  • ci: CI configuration files
  • docs: Documentation files

• Conditional job execution: Resource-intensive jobs only run when relevant files change:

  • security, test-rust, coverage-rust, msrv → rust-core changes
  • test-python, coverage-python → python changes
  • test-node, coverage-node → node changes
  • lint → always runs for fast feedback

• Full CI triggers:

  • All pushes to main branch
  • PRs with full-ci label

• Enhanced ci-success gate: Properly handles skipped jobs (success or skipped = pass)

Expected Performance Impact

Scenario	Before	After	Time Saved
Docs-only PRs	~15 min, 9 jobs	~2 min, 1 job	~87%
Python-only PRs	~15 min, 9 jobs	~8 min, 4 jobs	~47%
Node-only PRs	~15 min, 9 jobs	~8 min, 4 jobs	~47%
Core Rust PRs	Full CI	Full CI	0%
Main branch	Full CI	Full CI	0%

Test Plan

• Verify changes job correctly detects file changes
• Verify conditional jobs skip when not needed
• Verify full-ci label triggers all jobs
• Verify main branch pushes run full CI
• Verify ci-success correctly reports with skipped jobs

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@           Coverage Diff           @@
##             main      #14   +/-   ##
=======================================
  Coverage   78.80%   78.80%           
=======================================
  Files          27       27           
  Lines        4303     4303           
=======================================
  Hits         3391     3391           
  Misses        912      912           

Flag	Coverage Δ
rust-core	78.80% <ø> (ø)

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