feat(sync[dry-run]): auto-show all matched repos when filtering explicitly

[tony]

Summary

• Fix a confusing DX gap: vcspull sync tanstack-* --dry-run matched 5 repos but only displayed the 1 needing action — the 4 unchanged repos were hidden unless --show-unchanged was passed, even though the user had already scoped the command to specific repos.
• Add has_explicit_patterns to PlanRenderOptions: computed as not sync_all and bool(repo_patterns) in sync(), propagated to both the human and JSON/NDJSON render paths.
• Improve tip message: suppress the --show-unchanged hint when unchanged rows are already visible due to explicit filtering; show a shorter "run without --dry-run to apply" tip instead.
• Add xfail field and request.applymarker support to DryRunPlanFixture / test_sync_dry_run_plan_human for per-fixture conditional xfail without stopping test execution.

Design decisions

OR semantics at the call site: show_unchanged or has_explicit_patterns is passed to _filter_entries_for_display() rather than changing the function's own signature — the helper stays minimal and doesn't need to know about the concept of "explicit patterns".

--all unaffected: has_explicit_patterns is only True when repo_patterns is non-empty and sync_all is False. Bulk --all dry-runs retain the hide-unchanged default.

request.applymarker over pytest.xfail(): imperative pytest.xfail() short-circuits execution and can never become XPASS. request.applymarker applies the marker but still runs the test body, so the fixture transitions XFAIL → XPASS → PASS cleanly across the three-commit workflow.

Before / After

Before:

Progress: 5/5 +:0 ~:1 ✓:4 ⚠:0 ✗:0
Plan: 0 to clone (+), 1 to update (~), 4 unchanged (✓), 0 blocked (⚠), 0 errors (✗)

~/study/typescript/
  ~ tanstack-router  ~/study/typescript/tanstack-router  remote state unknown; use --fetch
Tip: run without --dry-run to apply. Use --show-unchanged to include ✓ rows.

After:

Progress: 5/5 +:0 ~:1 ✓:4 ⚠:0 ✗:0
Plan: 0 to clone (+), 1 to update (~), 4 unchanged (✓), 0 blocked (⚠), 0 errors (✗)

~/study/typescript/
  ~ tanstack-router  ~/study/typescript/tanstack-router  remote state unknown; use --fetch
  ✓ tanstack-devtools  ~/study/typescript/tanstack-devtools
  ✓ tanstack-store     ~/study/typescript/tanstack-store
  ✓ tanstack-table     ~/study/typescript/tanstack-table
  ✓ tanstack-virtual   ~/study/typescript/tanstack-virtual
Tip: run without --dry-run to apply.

Test plan

• unchanged-implicit-filter — --dry-run with explicit name pattern and pre-synced repo shows ✓ row without --show-unchanged
• unchanged-show — existing --show-unchanged flag still works
• uv run ruff check . --fix --show-fixes — no lint errors
• uv run ruff format . — no formatting changes
• uv run mypy — no type errors
• uv run py.test --reruns 0 — full suite passes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.32%. Comparing base (cfc5321) to head (6417c6f).

Additional details and impacted files

@@               Coverage Diff               @@
##           sync-edgecases     #540   +/-   ##
===============================================
  Coverage           83.31%   83.32%           
===============================================
  Files                  32       32           
  Lines                4496     4498    +2     
  Branches              904      904           
===============================================
+ Hits                 3746     3748    +2     
  Misses                499      499           
  Partials              251      251           

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