docs(changelog): consolidate 0.1.5-0.1.9 + ship 0.2.0 release notes

Add a comprehensive 0.2.0 section covering all 51 commits since v0.1.9.
Entries for 0.1.5 through 0.1.9 were skipped in the repo; this version
consolidates every wire-visible change into one entry.

Sections:

- Added: dev sandbox, smoke harness, structured logger,
  2.1.109/111/112/113 candidate manifests, Bun-native binary extraction,
  adaptive thinking wire shape, context-aware identity selector, Phase 1
  validation scenarios, check-beta-order.ts, Proxyman HAR tooling,
  capabilities snapshot, CLAUDE_CODE_ENTRYPOINT=sdk-cli default,
  long-context retry, wire-visible tool-name rewriting, account/org
  UUIDs in metadata.user_id.
- Changed: anthropic-beta emission order aligned with CC 2.1.113,
  src/betas.ts reorder, 19 silent catches filled with logger.debug(),
  plugin bundle renamed to .mjs, capture tooling migrated to TypeScript.
- Fixed: Haiku 4.5 beta inclusion fix, context-aware identity,
  identity-block cache-control TTL=1h, Sonnet 4.6+ 1M-context detection,
  Haiku 4.5+ structured outputs, account selection stickiness,
  cli.js import support.
- Known issues: cc_version suffix algorithm disproven (0/5 against real
  captures); impact LOW; documented in
  docs/mimese-http-header-system-prompt.md.

Format matches the existing Keep-a-Changelog style used through 0.1.4.
Pure addition; no churn on prior entries (git diff shows 50 insertions,
0 deletions).