feat: cwd.v1.context event + configurable project folder name #601

Summary

Track the work needed to implement proper CWD context propagation and configurable project folder naming.

Checklist

RFC updates

• Review existing IPC protocol RFC — add cwd.v1.context as an infrastructure-tier event (unbranded, stable contract)
• Document two-tier IPC namespace: infrastructure (cwd.v1.*, session.v1.*) vs capsule product (tool.v1.*, prompt_builder.v1.*)
• Define cwd.v1.context payload shape: { active, astrid_dirs }

Capsules — env-driven folder name (do first)

• Memory capsule: replace hardcoded .astrid with env::var("cwd_dir"), add cwd_dir to [env] onboarding fields in Capsule.toml
• Hook-bridge capsule: same
• Skills capsule: same
• Any other capsule that references .astrid by name: same

Distro

• Astralis Distro.toml: set cwd_dir = ".astrid" as shared env variable for all relevant capsules — so it is silently pre-filled and never shown to the user during astrid init

CLI (core)

• On session start, walk up from actual CWD collecting directories containing the value of cwd_dir
• Publish cwd.v1.context event before first prompt is processed
• Re-publish on CWD change (e.g. after tool execution resets CWD)

Capsules — cwd.v1.context subscription (do after CLI)

• Memory capsule: subscribe to cwd.v1.context, read from all discovered dirs, concatenate — replace hardcoded cwd:// path
• Hook-bridge capsule: subscribe to cwd.v1.context, load hooks from all discovered dirs
• Skills capsule: subscribe to cwd.v1.context, discover skills from all discovered dirs