docs: align repository guidance with extracted Engine and Next [skip ci]

Finish inherited guidance changes: point the existing sole prompt, turn-loop and remember references at the extracted Engine. Preserve the Next.js guidance generated by the installed version rather than leaving its ordinary dev-server write dirty.

Verified all three Engine paths exist and the complete generated Next block matches the unescaped template in web/node_modules/next/dist/server/lib/generate-agent-files.js; git diff --check passed. Documentation only; no tests or builds repeated. Root CW operator controls were not copied.

AGENTS.md

@@ -169,11 +169,11 @@ casually it reads as taking the work even when credit is preserved.
 - The model-facing subagent tool is `agent`; `agent_open`/`agent_eval`/
   `agent_close`/`delegate_to_agent` are removed surfaces. If the shape must
   move, move the code and its existing guard test with it.
-- `BASE_PROMPT` in `crates/tui/src/prompts/text.rs` is the sole base prompt
+- `BASE_PROMPT` in `crates/engine/src/prompts/text.rs` is the sole base prompt
   by convention. Same rule: move the code, not the prose, if that changes.
 - There is exactly one turn loop: `Engine::run_turn` in
-  `crates/tui/src/core/engine/turn_loop.rs`. Note that `crates/tui/src/core/`
-  is a module inside the TUI crate — it is not `crates/core`, which owns
+  `crates/engine/src/core/engine/turn_loop.rs`. Note that `crates/engine/src/core/`
+  is a module inside the engine crate (`codewhale-engine`) — it is not `crates/core`, which owns
   request construction, bounded fragments, and thread/session types and
   runs no turns. A guard test (`crates/core/tests/single_turn_loop.rs`)
   fails on a second loop; changing the shape means changing the guard
@@ -184,7 +184,7 @@ casually it reads as taking the work even when credit is preserved.
   volatile fact into the prefix; append it as a user-role message.
 - These active modules are repeatedly misidentified as dead; verify consumers
   before removal: `runtime/src/context_budget.rs`,
-  `runtime/src/prompt_zones.rs`, `tui/src/tools/remember.rs`, and
+  `runtime/src/prompt_zones.rs`, `engine/src/tools/remember.rs`, and
   `config/src/route/`. Native memory lives in `runtime/src/native_memory.rs`;
   `tools/remember.rs` is its capture path.
 - Environment-specific behavior belongs in `docs/ENVIRONMENTS.md`, not here.

web/AGENTS.md

@@ -40,3 +40,13 @@ npm test
 npm run lint
 npm run build
 ```
+
+<!-- BEGIN:nextjs-agent-rules -->
+
+## This is NOT the Next.js you know
+
+This version has breaking changes — APIs, conventions, and file structure may all differ from your training data. Read the relevant guide in `node_modules/next/dist/docs/` (resolved from this file's directory; in monorepos the `next` package may not be visible from the repo root) before writing any code. Heed deprecation notices.
+
+This block is written and re-added by `next dev` — verify at `node_modules/next/dist/server/lib/generate-agent-files.js`. Removing it from a diff only re-creates the uncommitted change; committing it with your work keeps the tree clean.
+
+<!-- END:nextjs-agent-rules -->