feat(routing): canonicalize model names before [[models]] lookup

[Destynova2]

Summary

• Add routing::classify::model_name::canonicalize_model_name and call it as step 0 of Router::route, so cosmetic variations of provider model IDs collapse to a single canonical key before any subsequent step (background regex, auto-map, prompt rules, [[models]] lookup).
• Idempotent and zero-allocation on already-canonical inputs (Cow::Borrowed), so configs that use the canonical IDs (gpt-4o, claude-sonnet-4-5, …) pay nothing.
• Bump the 7 enterprise preset snapshots whose default_non_claude row now carries the canonicalized gpt-5-2 instead of gpt-5.2.

Rules (in order)

1. Lowercase ASCII.
2. Strip trailing -latest.
3. Strip trailing -YYYYMMDD (exactly 8 digits — guards gpt-5-2).
4. <digit>.<digit> to <digit>-<digit>, gated on a known family prefix (claude-, gpt-, gemini-, grok-, deepseek-) so unrelated IDs like glm-4.6 survive untouched.
5. Anthropic family-version reorder: claude-{N}-{M}-{family} → claude-{family}-{N}-{M} so older claude-3-5-sonnet and modern claude-sonnet-4-5 spellings collapse into one key (matching the spelling used in presets/*.toml).

Why this base branch

Based on fix/preset-mod-include-str (PR #304) because main does not currently build (referenced presets/{medium,local,cheap,fast}.toml files were deleted but include_str! calls remain). Will rebase to main automatically once #304 lands.

Test plan

• 25-row coverage matrix in model_name.rs exercises Anthropic 3.x/4.x, OpenAI (gpt-4o, gpt-5, gpt-5-2, gpt-5.2), DeepSeek, Gemini, Grok families.
• Proptest verifies idempotence over arbitrary alphanumeric inputs (regression seed for 0.0.0 checked in).
• All 130 existing routing tests pass (including the regression guards test_auto_map_skips_explicit_virtual_model and test_no_auto_map_non_matching — glm-4.6 is unaffected by rule 4 thanks to the family-prefix gate).
• All 1263 lib + integration tests pass.
• cargo fmt --check, cargo clippy --all-targets -- -D warnings, and cargo nextest run all green locally.