Refactor internal request state into DispatchContext

[alganet]

Replace the old local Request wrapper with an explicitly internal DispatchContext built around the PSR-7 server request.

Changes:

• rename src/Request.php to src/DispatchContext.php
• keep the PSR request as the canonical transport object via $request
• replace shadow request fields with explicit context accessors and mutators for effective method/path
• rename Router::$request to Router::$context
• rename Router::dispatchRequest() to Router::dispatchContext()
• update router dispatch flow, routes, and routines to accept DispatchContext instead of the misleading Request type
• migrate tests and stubs to the new terminology and API
• add router regressions for empty global OPTIONS handling and Router stringification through the active dispatch context

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 97.14%. Comparing base (e2a76c4) to head (f4ba645).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #165      +/-   ##
============================================
+ Coverage     96.46%   97.14%   +0.67%     
- Complexity      441      445       +4     
============================================
  Files            27       27              
  Lines          1076     1085       +9     
============================================
+ Hits           1038     1054      +16     
+ Misses           38       31       -7     

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