Remove PROVIDER environment variable from Dockerfile

[yookoala]

Summary

Describe this PR in 2-5 bullets:

• as detailed in [Bug]: Unable to use Mistral provider after restart #831, the provider settings in config.toml is ignored because a fixed PROVIDER environment variable is set.
• avoid having default provider in dockerfile would prevent provider settings in config.toml being ignored.

Label Snapshot (required)

• Risk label: medium
• Size label: S
• Scope labels: provider, dev
• Module labels: dockerfile
• Contributor tier label: experienced contributor
• If any auto-label is incorrect, note requested correction:

Change Metadata

• Change type bug|feature|refactor|docs|security|chore): bug
• Primary scope (runtime|provider|channel|memory|security|ci|docs|multi):

Linked Issue

• Closes [Bug]: Unable to use Mistral provider after restart #831
• Related #
• Depends on # (if stacked)
• Supersedes # (if replacing older PR)

Supersede Attribution (required when Supersedes # is used)

• Superseded PRs + authors (#<pr> by @<author>, one per line):
• Integrated scope by source PR (what was materially carried forward):
• Co-authored-by trailers added for materially incorporated contributors? (Yes/No)
• If No, explain why (for example: inspiration-only, no direct code/design carry-over):
• Trailer format check (separate lines, no escaped \n): (Pass/Fail)

Validation Evidence (required)

Commands and result summary:

docker build -f Dockerfile -t zeroclaw
docker run -it --rm --volume=zeroclaw-data:/zeroclaw-data --name=zeroclaw zeroclaw onboard --api-provider=mistral ....
docker run -it --rm --volume=zeroclaw-data:/zeroclaw-data --name=zeroclaw -d zeroclaw gateway
docker exec zeroclaw zeroclaw doctor

• Evidence provided (test/log/trace/screenshot/perf):
• If any command is intentionally skipped, explain why:

Security Impact (required)

• New permissions/capabilities? No
• New external network calls? No
• Secrets/tokens handling changed? No
• File system access scope changed? No
• If any Yes, describe risk and mitigation:

Privacy and Data Hygiene (required)

• Data-hygiene status (pass|needs-follow-up):
• Redaction/anonymization notes:
• Neutral wording confirmation (use ZeroClaw/project-native labels if identity-like wording is needed):

Compatibility / Migration

• Backward compatible? (Yes/No)
• Config/env changes? (Yes/No)
• Migration needed? (Yes/No)
• If yes, exact upgrade steps:

i18n Follow-Through (required when docs or user-facing wording changes)

• i18n follow-through triggered? (Yes/No)
• If Yes, locale navigation parity updated in README*, docs/README*, and docs/SUMMARY.md for supported locales (en, zh-CN, ja, ru, fr, vi)? (Yes/No)
• If Yes, localized runtime-contract docs updated where equivalents exist (minimum for fr/vi: commands-reference, config-reference, troubleshooting)? (Yes/No/N.A.)
• If Yes, Vietnamese canonical docs under docs/i18n/vi/** synced and compatibility shims under docs/*.vi.md validated? (Yes/No/N.A.)
• If any No/N.A., link follow-up issue/PR and explain scope decision:

Human Verification (required)

What was personally validated beyond CI:

• Verified scenarios:
• Edge cases checked:
• What was not verified:

Side Effects / Blast Radius (required)

• Affected subsystems/workflows:
• Potential unintended effects:
• Guardrails/monitoring for early detection:

Agent Collaboration Notes (recommended)

• Agent tools used (if any):
• Workflow/plan summary (if any):
• Verification focus:
• Confirmation: naming + architecture boundaries followed (AGENTS.md + CONTRIBUTING.md):

Rollback Plan (required)

• Fast rollback command/path:
• Feature flags or config toggles (if any):
• Observable failure symptoms:

Risks and Mitigations

List real risks in this PR (or write None).

• Risk:
  • Mitigation:

[github-actions]

PR intake checks found warnings (non-blocking)

Fast safe checks found advisory issues. CI lint/test/build gates still enforce merge quality.

• Incomplete required PR template fields: summary problem, summary why it matters, summary what changed, security risk/mitigation

Action items:

1. Complete required PR template sections/fields.
2. Remove tabs, trailing whitespace, and merge conflict markers from added lines.
3. Re-run local checks before pushing:
   • ./scripts/ci/rust_quality_gate.sh
   • ./scripts/ci/rust_strict_delta_gate.sh
   • ./scripts/ci/docs_quality_gate.sh

Run logs: https://github.com/zeroclaw-labs/zeroclaw/actions/runs/22252077250

Detected blocking line issues (sample):

• none

Detected advisory line issues (sample):

• none

[chumyin]

Completed review and finalization for this PR.

What this change does:

• Removes the hard-coded Docker PROVIDER default so runtime config in config.toml is not silently overridden by container env defaults.

Validation status:

• Fork workflow runs were re-triggered by maintainer.
• CI checks are now green, including Detect Change Scope, Non-Rust Fast Path, and CI Required Gate.

We are conducting automation testing, and this issue or PR is actually being handled automatically by ZeroClaw. If anything goes wrong or you have any questions, please contact @chumyin directly for better assistance.