fix: remove env vars not recognized by arkd

[Dunsin-cyber]

fixes #18

ARKD_SCHEDULER_TYPE and ARKD_ALLOW_CSV_BLOCK_TYPE never existed as config keys in arkd — the scheduler type is derived automatically from the VtxoTreeExpiry locktime type. ARKD_ROUND_INTERVAL was a DB column that was renamed to SESSION_DURATION; ARKD_SESSION_DURATION already covers this correctly.

[arkanaai]

✅ LGTM — Approve

Verified against arkd source: ARKD_SCHEDULER_TYPE, ARKD_ALLOW_CSV_BLOCK_TYPE, and ARKD_ROUND_INTERVAL have zero references in the arkd codebase. These are dead env vars — passing them to arkd does nothing.

What the PR does

Removes three stale environment variables from all three locations they appeared:

• .env.defaults — default values removed
• docker/docker-compose.arkd-override.yml — container env passthrough removed
• start-env.sh — shell exports removed

Correctness check

• ARKD_SESSION_DURATION (kept) is the real config key — confirmed in arkd/README.md, arkd/Makefile, arkd/envs/arkd.light.env, and arkd/docker-compose.regtest.yml. ✅
• ARKD_ROUND_INTERVAL (removed) — zero matches in arkd. The PR description says it was renamed; SESSION_DURATION covers this. ✅
• ARKD_SCHEDULER_TYPE (removed) — zero matches in arkd. Scheduler type is derived from the VtxoTreeExpiry locktime type. ✅
• ARKD_ALLOW_CSV_BLOCK_TYPE (removed) — zero matches in arkd. Never existed as a config key. ✅

Completeness

All three files in this repo that reference the removed vars are updated. No dangling references remain. Grep confirms clean removal.

Note (out of scope)

Two other repos still set ARKD_SCHEDULER_TYPE: arkd-pentester/docker-compose.yml and introspector-review/docker-compose.regtest.yml. Same cleanup could be applied there separately.

Not protocol-critical

This change only removes no-op env var passthrough in a regtest harness. No VTXO handling, signing, forfeit paths, or exit logic is affected.

🤖 Reviewed by Arkana

[Dunsin-cyber]

Hi, @Kukks, is this good to go?