Add SegmentedNumber, CyclicCounter, and numeric footprint docs

[NikolayChirkov]

Summary

• Add header-only SegmentedNumber (ae::seg::Format / Compile) for piecewise-quantized physical values with Formula encode/decode over FixedPoint (Rep width <= 32), no per-code lookup tables.
• Add CyclicCounter<Wire,Value>: full local counter, truncated wire bits, contextual restore/advance only (stateless deserialize does not compile).
• Document ESP32-C6 footprints, constant tables, object/stack sizes, and desktop benchmarks; add tools/measure_esp32c6_footprint.py and tools/generate_footprint_docs.py.

Test plan

• GCC Debug + Release (ctest, warnings as errors)
• Clang Debug + Release
• MSVC Debug + Release
• ESP32-C6 object footprint -Os / -O2 (see docs/footprint.md)
• Desktop numeric-bench (see docs/benchmarks.md)
• CI matrix on this PR

[NikolayChirkov]

Reviewer request: Anton Kitaev. GitHub profile realkoldun (display name Anton Kitaev) is not a collaborator on this repo, so the formal review request is assigned to @BartolomeyKant. Please reassign if Anton should review under a different login.

[BartolomeyKant]

While those types are not trivial to understand it should be properly documented.
Start each file with short description:

• motivation
• known analogous if any?
• brief description how to use
• brief description how it works

[NikolayChirkov]

Addressed the documentation request in 7db38b0aeb465c9de9def37e9bcf8608ddc70afb.

Added file-level architecture overviews to the public and internal numeric headers. Each overview now covers the motivation, related/analogous concepts, brief usage, how the implementation works, and the important invariants or public/internal boundary.

The documentation covers CyclicCounter, the SegmentedNumber public API and wire/floating adapters, the schema/curve/compiler/formula layers, and the shared FixedPoint/integer math layers. This commit changes comments only: no API, wire ABI, algorithms, schema hashes, numeric constants, or generated data changed.

The documentation commit is a single clean commit on top of the CI cleanup. git diff --check passed; the full PR CI matrix has been triggered for the new head.

[NikolayChirkov]

Addressed the five review threads in 7ce31f7:

• generalized integral/TieredInt rank conversion;
• added SegmentedFormatSpec;
• added explicit integral-like CyclicCounter arithmetic;
• unified segmented internals under ae::seg::detail;
• documented and enforced the intentional 32-bit Formula backend boundary.

All local compiler configurations (GCC/Clang/MSVC Debug+Release), compile-fail tests, cpplint, and golden wire tests pass. GitHub Actions: in progress (run 33556521462).