Postmaster v9.4.4: WebGUI-only task correction

[the-code-learner]

Summary

Correct v9.4.3 forward without rewriting the immutable historical release.

• restore the public task MCP/backend contract exactly to v9.4.2 compatibility;
• keep list_jobs(owner_id=None, project_id=None, status=None, limit=200) with no include_completed;
• include completed tasks by default through MCP and restore pre-v9.4.3 serialization;
• keep one canonical get_job registration only;
• restore SchedulerEngine.list_jobs to v9.4.2 semantics;
• remove the v9.4.3 task-detail/default-hide capability flags;
• implement completed hide/show and full task detail only in the WebGUI using show_completed=1 / view_job=<id> while preserving the Tasks tab;
• retain Pause/Resume behavior, recurring/task persistence, approval/security, mail/account/knowledge/tracking/file behavior;
• keep postmaster-mcp.yml byte-for-byte unchanged.

Pre-PR verification

• base main: c7d24fd98d3439f922ef55fc724e6b359a7279eb (VERSION=9.4.3)
• branch HEAD: 4f9ce403121bb3979fd2e4da3afbb03318c776a4
• branch is ahead by 3, behind by 0
• no open conflicting PRs were found
• no v9.4.4 tag ref resolves
• src/postmaster/runtime_core.py blob is identical to v9.4.2 runtime.py
• src/postmaster/scheduler_engine.py blob is identical to v9.4.2
• postmaster-mcp.yml blob 2347745cd85a79d894aba0e333e599f874675e29 matches the v9.4.2 baseline
• pre-PR audit corrected an accidental README truncation and a regression-test target mistake without changing backend semantics

Required validation

The required v9 runtime tests / test check must cover the v9.4.2 MCP schema/output contract, completed-default visibility, single get_job, WebGUI hide/show/detail/counts, Pause/Resume, scheduler status/due/complete/recurring behavior, full existing regression suites, provider-neutral/privacy scan, and single-YAML bootstrap behavior.