docs: prepublish v0.1.0 — README rewrite, changelog, packaging, doc statuses

- README rewritten in alktty's shape: quick start (producer dial +
  listen, consumer open/reverse/pump), the role table, the
  resource-not-an-address model, the data-plane summary, features +
  wasm sections — examples mirror tests/harness.rs wiring
- CHANGELOG.md added (0.1.0 entry, Keep a Changelog house style)
- tasks/ added to the package exclude (was shipping 16 internal SDD
  task notes; package 50 -> 35 files)
- docs/architecture spec docs: status draft -> implemented (Phase 2
  complete, review 001 remediated)

Verified: 71 tests default / 91 --features local, clippy -D warnings
(all-targets + wasm32), fmt, cargo doc warning-free,
wasm32-unknown-unknown check, publish dry-run (35 files, 406.2KiB)

Cargo.toml

@@ -9,7 +9,7 @@ repository = "https://git.alk.dev/alkdev/alktunnels"
 readme = "README.md"
 keywords = ["tunnel", "proxy", "channels", "alkcall", "network"]
 categories = ["network-programming", "asynchronous"]
-exclude = [".opencode/", "AGENTS.md", "docs/reviews/", "docs/research/", "docs/plans/", "docs/sdd_process.md"]
+exclude = [".opencode/", "AGENTS.md", "docs/reviews/", "docs/research/", "docs/plans/", "tasks/", "docs/sdd_process.md"]
 
 [lib]
 name = "alktunnels"