Add HTTP/3 frame codec support in istok-core (#2)

* docs: remove extra workspace and tighten offline cargo policy

* Added workspace-level Cargo.lock; fixed compile errors

* updated AGENTS.md

* updated AGENTS.md

Author: RomanEmreis

.codex/skills/milestone_playbook.md

@@ -5,5 +5,6 @@ Each milestone task must define:
 - Acceptance tests (unit/integration)
 - DoD checklist
 - Notes on no_std/min-deps impact
+- Scaffold files are part of the design; do not remove unless asked.
 
 Prefer vertical slices: "end-to-end minimal" over "perfect subsystem".

.gitignore

@@ -18,4 +18,4 @@ target
 #  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
 #  and can be added to the global gitignore or merged into this file.  For a more nuclear
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
-#.idea/
+.idea/

AGENTS.md

@@ -46,4 +46,19 @@ M4: Backpressure, memory discipline, performance profiling & metrics hooks
 - `cargo run -p istok-server --example h3_hello`
 
 ## Decision log
-Architecture-affecting decisions must be captured in `docs/rfcs/` before large refactors.
+Architecture-affecting decisions must be captured in `docs/rfcs/` before large refactors.
+
+## Scaffolding is intentional
+- Do NOT delete or collapse placeholder modules/files (even if currently unused).
+- Keep the planned crate/module structure stable.
+- If something is unused, prefer leaving it in place with a short comment, or gate it behind a feature.
+- Any removal/renaming of scaffold files requires an RFC or explicit instruction.
+
+## Reproducible builds & network
+- Network access is available, but keep builds reproducible.
+- Never set `RUSTUP_TOOLCHAIN` and never use `cargo +<toolchain>`.
+- Do not modify workspace members to “fix” build issues.
+- Always run Cargo commands with `--locked` (tests, clippy, build).
+- Do not update `Cargo.lock` unless explicitly requested.
+- New dependencies require a short justification and must be minimal.
+- `istok-core` must remain `no_std`-friendly: avoid `std`-only deps there; prefer `default-features = false`.