S24.08: enforce top-down function ordering across all source files

[DavidCozens]

Parent epic: #254

Motivation

CLAUDE.md mandates a top-down function-ordering rule:

Within a source file, functions are ordered top-down so the reader sees
the lifecycle and public API first, then drills into helpers as they
appear: `_Create` first, `_Destroy` second, public functions after,
helper functions are forward-declared at the top of the file and
defined immediately beneath the function that first calls them.

In practice almost every E11 pool-class `Static.c` violates the
"defined immediately beneath their first caller" half of the rule —
`_IndexFromHandle` / `*_CleanupAtIndex` (and similar pool helpers)
are grouped at the file end after `_Create` and `_Destroy`. This
came to light when CodeRabbit flagged `SolidSyslogPosixAddressStatic.c`
on PR #422 and the only honest defence was "matches every other
pool-class". I.e. the convention has drifted, not the new file.

This story tightens the whole tree to the documented rule in one pass.

Scope

All `.c` files under:

• `Core/Source/` — every `Static.c` plus any `.c` that has helpers
  defined out of order
• `Platform/{Posix,Windows,FreeRtos,Atomics,OpenSsl,MbedTls,FatFs}/Source/`
• `Bdd/Targets/` C sources (best effort — these are Tier 3)

Tests (`Tests/`) out of scope — the test fixture grouping doesn't follow
the same rule.

Acceptance criteria

• Every `*Static.c` pool-class file has `_Create` first, `_Destroy`
  second, then each helper immediately beneath its first caller
  (forward declarations at the top as needed).
• Same for the non-Static.c production sources where helpers are
  currently grouped at file end (`SolidSyslog.c`, `SolidSyslogFormatter.c`,
  RecordStore.c`, etc. — audit on entry to the story).
• No behaviour change. Diff is move-only.
• CI green on all platforms.
• Diff reviewed against the rule, not against existing precedent.

Out of scope

• `Tests/` — fixture lifetime macros impose a different layout
• Header files