[Nithin Jose (nijosmsft)]

Description

Addresses focused review feedback for the tiered range implementation stacked in #6410.

• Uses direct capacity arithmetic for tiered indexing.
• Uses bulk moves for block-local insertions and removals.
• Uses wider working values while retaining compact stored fields.
• Simplifies narrowing casts and allocation comments.
• Calls the production stream ACK handler directly from unit tests.
• Adds contributor documentation for the final range architecture and ownership model.

Stack:

1. Implement tiered storage for large QUIC ranges #6391 — tiered range implementation
2. Refactor tiered and array range implementations #6410 — storage encapsulation and policy
3. This PR — focused review cleanups and documentation

Testing

• Debug and Release x64 Schannel builds.
• Debug x64 kernel solution build.
• Full Debug x64 Schannel BVT: 3,436 tests ran, 107 skipped, zero failures or controller errors.
• Ubuntu 24.04 GCC 13.3 and Clang 18.1 incremental Debug rebuilds with quictls, LTTng logging, tests enabled, and -Werror -Wall -Wextra.
• Generated Linux CLOG/LTTng trace sources compiled successfully.
• CLOG regeneration produced no source changes.

Documentation

Adds docs/contrib/Range.md covering representations, invariants, promotion, demotion, ownership, lifecycle, and mutation behavior.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.37%. Comparing base (508e329) to head (817bbd1).

Additional details and impacted files

@@                        Coverage Diff                        @@
##           nijosmsft/range_tier_refactor    #6411      +/-   ##
=================================================================
+ Coverage                          88.23%   88.37%   +0.13%     
=================================================================
  Files                                 64       64              
  Lines                              19393    19400       +7     
=================================================================
+ Hits                               17112    17145      +33     
+ Misses                              2281     2255      -26     

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[Copilot]

🟢 Approval recommended

No unresolved issues remain, and the reported model checks support the revised circular-block movement logic.

No open issues 🎉

What changed in this PR

This PR refines the tiered range implementation introduced in the preceding stack, simplifying storage operations and documenting the architecture without changing the intended range semantics.

Changes:

• Replaces shift-and-mask indexing with capacity arithmetic and block-local loops with bulk moves.
• Removes the stream ACK test shim so unit tests call the production handler directly.
• Documents range storage, invariants, ownership, and lifecycle transitions.

File	Description
src/​core/​unittest/​StreamAckTestShim.c	Deletes the redundant ACK handler wrapper.
src/​core/​unittest/​RangeTest.cpp	Calls the production stream ACK handler directly.
src/​core/​unittest/​CMakeLists.txt	Removes the deleted shim from test sources.
src/​core/​stream.h	Adds C linkage guards for C++ callers.
src/​core/​range_tiered.h	Simplifies block and directory capacity constants.
src/​core/​range_tiered.c	Uses capacity arithmetic, wider working values, and bulk local moves.
docs/​contrib/​Range.md	Documents range architecture and ownership.

_{Review effort: Balanced}