feat: add protocol comparison docs, P2P crate, production audit, and design fixes

Add comprehensive documentation comparing quicnprotochat against classical
chat protocols (IRC+SSL, XMPP, Telegram) with diagrams and attack scenarios.
Promote comparison pages to top-level sidebar section. Include P2P transport
crate (iroh), production readiness audit, CI workflows, dependency policy,
and continued architecture improvements across all crates.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/CODEOWNERS

@@ -0,0 +1,15 @@
+# Code owners for quicnprotochat. PRs require review from owners.
+# See https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners
+# Replace 'maintainers' with your GitHub user/team handle.
+
+# Default owners for everything in the repo
+* @maintainers
+
+# Crate-specific (uncomment and add handles when you have designated owners)
+# /crates/quicnprotochat-core/     @owner1
+# /crates/quicnprotochat-proto/    @owner1
+# /crates/quicnprotochat-server/   @owner1
+# /crates/quicnprotochat-client/   @owner1
+# /crates/quicnprotochat-p2p/      @owner1
+# /schemas/                        @owner1
+# /docs/                           @owner1

.github/workflows/ci.yml

@@ -0,0 +1,74 @@
+name: CI
+
+on:
+  push:
+    branches: [main, master]
+  pull_request:
+    branches: [main, master]
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-action@stable
+        with:
+          components: clippy, rustfmt
+
+      - name: Install capnp
+        run: sudo apt-get update && sudo apt-get install -y capnproto
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-
+
+      - name: Check format
+        run: cargo fmt --all -- --check
+
+      - name: Build
+        run: cargo build --workspace
+
+      - name: Test
+        run: cargo test --workspace
+
+      - name: Clippy
+        run: cargo clippy --workspace --all-targets --
+
+  deny:
+    name: cargo-deny
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install cargo-deny
+        run: cargo install cargo-deny --locked
+
+      - name: Check deny
+        run: cargo deny check
+
+  audit:
+    name: cargo-audit
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-action@stable
+
+      - name: Run audit
+        run: |
+          cargo install cargo-audit --locked
+          cargo audit