refactor(pathfinder): author candidates in search order

[rwgk]

Description

Follow-up to #2689 and the ordering discussion in
#2689 (comment).

Pathfinder historically authored dynamic-library filenames in ascending order,
then reversed them at each runtime lookup site. That distinction no longer
serves the descriptor catalog and makes preference mistakes easier.

This PR:

• authors Linux SONAMEs and Windows DLL names directly in runtime preference
  order, most preferred first;
• makes filesystem discovery, already-loaded detection, and native loader
  search consume the descriptor tuples as-is;
• preserves the historical order of the private legacy SUPPORTED_*
  projections at their compatibility boundary; and
• documents that ordered candidates for dynamic libraries, headers, binary
  utilities, static libraries, and bitcode libraries are consumed first to
  last.

The tuple rewrite is mechanically behavior-neutral: every multi-name dynamic
library tuple is the exact reverse of its previous catalog representation, and
the corresponding runtime reversal is removed.

Validation

• New or existing tests cover these changes.
• The documentation is up to date with these changes.
• Full cuda-pathfinder suite: 1,608 passed, 5 skipped on CUDA 13.3.
• Repository-wide pre-commit suite (excluding the network-only link
  checker).

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[rwgk]

/ok to test e7705a7