perf: pre-compile session-key regex

[Ray0907]

Summary

• Pre-compile regex patterns in session-key normalization functions to avoid repeated compilation on
  every call

Test plan

• pnpm test src/routing/session-key.test.ts passes

[thewilloftheshadow]

Squash-merged into main.

• Squash commit: 73507e8
• Included: precompiled session key regexes + changelog entry (thanks)
• Tests: pnpm lint && pnpm build && pnpm test (lint failed in existing src/line/* types)

[thewilloftheshadow]

Closed after squash-merge to main (commit 73507e8).