feat(workspace): report worktree disk cleanup pressure

[chubes4]

Summary

• Add disk-pressure reporting to workspace worktree list/cleanup output: estimated sizes, age, stale reason, artifact profiles, top repo/worktree summaries, and size/age cleanup sorting.
• Keep cleanup destructive behavior conservative while surfacing non-destructive artifact visibility for large build/cache directories.
• Expand cleanup GitHub PR lifecycle detection so bounded cached lookups distinguish merged PRs from closed-unmerged PRs.

Incident context

On 2026-04-29, /Users/chubes/Developer had 787 worktree-like directories using about 712.6 GiB. homeboy@* alone accounted for 215 directories and about 592.0 GiB; removing 208 clean Homeboy worktrees freed about 572.7 GiB.

This PR makes that kind of pressure visible before cleanup becomes an emergency, without loosening the existing dirty/unpushed safety gates.

Changes

• Adds disk metadata to worktree list rows: size_bytes, estimated_size_bytes, last_touched_at, age_days, artifact_size_bytes, artifacts, and stale_reason.
• Adds --stale to workspace worktree list for quick old/dirty/missing-metadata review.
• Adds cleanup summary totals and repo buckets for worktree size and artifact size, plus top_by_size / top_by_age JSON summaries.
• Adds --sort=size|age for cleanup candidate ordering.
• Adds non-destructive artifact profile reporting for Rust target, Node build/dependency caches, and Composer vendor, with a datamachine_code_worktree_artifact_profile filter.
• Changes GitHub cleanup lookup from merged-only to closed same-repo PRs so merged branches get pr-merged and closed-unmerged branches get pr-closed.

Tests

• php -l inc/Workspace/Workspace.php && php -l inc/Cli/Commands/WorkspaceCommand.php && php -l inc/Abilities/WorkspaceAbilities.php && php -l tests/smoke-worktree-cleanup-cli.php && php -l tests/smoke-worktree-cleanup.php && php -l tests/smoke-worktree-cleanup-github-cache.php
• php tests/smoke-worktree-cleanup-cli.php
• php tests/smoke-worktree-cleanup.php
• php tests/smoke-worktree-cleanup-github-cache.php
• php tests/smoke-worktree-lifecycle-metadata.php
• git diff --check

Focused homeboy lint --file runs still report existing PHPStan baseline issues in the large touched files; PHPCS formatting is clean for the production files touched by this PR.

Closes #144
Refs #142
Refs #145

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Implemented the cleanup reporting changes, updated smoke coverage, ran focused verification, and drafted this PR description. Chris remains responsible for review and merge.