docs: Apply en-GB Oxford spelling and sentence case corrections to design document

[coderabbitai]

Overview

This issue tracks additional spelling and style corrections needed for docs/lag-complexity-function-design.md to align with the repository guideline "en-GB-oxendict (-ize / -our)".

Required Corrections

1. Line 24-31: Adopt en-GB Oxford spelling

Change: prioritises → prioritizes

- problem-solving, LAG introduces a "reasoning-first" pipeline that prioritises
+ problem-solving, LAG introduces a "reasoning-first" pipeline that prioritizes

2. Line 84-89: Use Oxford -ize spelling

Change: optimised → optimized

- benchmarked and optimised for performance, a critical requirement for a
+ benchmarked and optimized for performance, a critical requirement for a

3. Line 265-268: Fix trait names and use Oxford -ize

Changes:

• Fix trait names: Serialise/Deserialise → Serialize/Deserialize
• Change prose: deserialisable → deserializable

- variant, Variance, accepts a window size and all configuration types derive
- Serialise/Deserialise for convenient loading.
+ variant, Variance, accepts a window size and all configuration types derive
+ Serialize/Deserialize for convenient loading.

- way to tune the behaviour of the scoring engine. The entire structure will be
- deserialisable from a TOML file using serde, allowing operators to adjust
+ way to tune the behaviour of the scoring engine. The entire structure will be
+ deserializable from a TOML file using serde, allowing operators to adjust

4. Line 268-277: Use Oxford -ize for nouns

Change: normalisation → normalization

- - Sigma: An enum representing the normalisation strategy. This provides
+ - Sigma: An enum representing the normalization strategy. This provides

5. Line 320-335: Use Oxford -ize spelling

Change: prioritising → prioritizing

- The selection of default features is a deliberate design choice prioritising
+ The selection of default features is a deliberate design choice prioritizing

6. Line 336-338: Write headings in sentence case

Change: Convert table heading to sentence case

- #### Table 1: Feature Flag Specification
+ #### Table 1: Feature flag specification

7. Line 550-556: Sentence case and Oxford -ize for headings

Changes: Apply sentence case and normalization spelling

- ## 3. Configuration Deep Dive: Normalisation, Scheduling, and Halting
+ ## 3. Configuration deep dive: normalization, scheduling, and halting

Context

These corrections were identified during review of PR #11: #11

Reference: #11 (comment)

Acceptance Criteria

• All 7 spelling corrections applied to docs/lag-complexity-function-design.md
• Documentation follows en-GB Oxford spelling (-ize family) consistently
• Headings use sentence case formatting
• Rust trait names use correct spelling (Serialize/Deserialize)
• Changes pass make markdownlint validation