docs: require per-agent commit attribution; add Swift guidelines

AGENTS.md: replace the 'no AI attribution footers' rule with a requirement that every agent-authored/co-authored commit end with a Co-Authored-By trailer naming the specific agent/model. Add docs/SWIFT_GUIDELINES.md to the repo layout.

docs/SWIFT_GUIDELINES.md: consolidate the team Swift standards (coding style, testing, patterns, security, tooling hooks) into a self-contained project doc, with project notes for Xcode MCP, MainActor/Sendable, and SwiftData gotchas.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

AGENTS.md

@@ -42,6 +42,8 @@ OpenAppLockUITests/             XCUITest flows (see harness below)
 docs/RULES_FEATURE_SPEC.md  Feature spec derived from the Opal reference
                             recording; §6 maps it to the native presentation.
                             Review/update this BEFORE behavior changes.
+docs/SWIFT_GUIDELINES.md    Swift coding/testing/patterns/security standards
+                            agents must follow on this project.
 ```
 
 ## Domain facts worth knowing
@@ -81,8 +83,12 @@ docs/RULES_FEATURE_SPEC.md  Feature spec derived from the Opal reference
   changes, write the failing test, run it (compile failure counts as red),
   implement, re-run focused tests, then the full suite. Run tests often and
   fail fast.
-- Conventional commits (`feat:`, `fix:`, `refactor:` …), no AI attribution
-  footers. Commit only when the user asks.
+- Conventional commits (`feat:`, `fix:`, `refactor:` …). **Agent attribution is
+  required**: every commit an agent authors or co-authors must end with a
+  `Co-Authored-By:` trailer naming the specific agent/model that did the work,
+  added manually in the commit message — e.g.
+  `Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>` (a
+  non-Claude agent uses its own name/email). Commit only when the user asks.
 
 ## UI-test harness