Extract staged routine execution into RoutinePipeline

[alganet]

Formalize the when/by/through lifecycle behind a dedicated pipeline so routine orchestration no longer lives in scattered route and context methods.

Changes:

• add RoutinePipeline to own:
  • when-stage route gating
  • by-stage pre-handler routine execution
  • through-stage post-handler transformation
• make DispatchEngine use RoutinePipeline for match-time routine checks
• make DispatchContext use the pipeline for pre/post route execution
• remove routine-stage orchestration from DispatchContext
• remove AbstractRoute::matchRoutines() now that when-stage execution is owned by the pipeline
• keep forwarding, response short-circuiting, and through-transform behavior intact under the new staged abstraction

Verification:

• composer qa
• changed executable lines verified at 100% coverage

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.88%. Comparing base (baa45eb) to head (c340a3d).

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #167      +/-   ##
============================================
- Coverage     96.89%   96.88%   -0.01%     
- Complexity      450      452       +2     
============================================
  Files            28       29       +1     
  Lines          1096     1093       -3     
============================================
- Hits           1062     1059       -3     
  Misses           34       34              

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