Bound targeted workspace show probes

[chubes4]

Closes #1212

Summary

• keep targeted show on one exact target probe and avoid per-worktree filesystem probes while retaining aggregate capacity count
• record target filesystem/Git and show-phase timings without expanding the public response
• prove a 176-worktree workspace performs only the target checkout Git probes and no unrelated worktree probes

Verification

• php tests/workspace-command-startup-bounds.php
• php tests/workspace-show-cli-format-contract.php
• php tests/worktree-disk-budget.php
• php tests/workspace-ability-registration-integration.php
• php tests/workspace-primary-network-freshness.php
• php tests/workspace-list-bounded-contract.php
• changed-file PHP syntax checks
• git diff --check

AI Assistance

OpenAI GPT-5.6 Sol via OpenCode traced the targeted show path, implemented the bounded aggregate and phase evidence, built the 176-worktree call-count proof, and ran the listed gates under human orchestration.