A malformed marker crashed the courtesy URL, and the hint guessed the port

[Shashankss1205]

Three defects in the watch-line plumbing

watch_url() reads .grapharc/live-server.json to print the exact live-view URL for a run, and watch_hint() prints the instruction when no server answers. Three gaps, all found by walking the marker lifecycle:

1. Two marker shapes escaped as tracebacks. The tolerant read caught OSError, ValueError, KeyError — but a marker containing "port": null (int(None)) or a non-object JSON document (indexing a list) raises TypeError, which flew straight out of a command whose only job at that moment was printing a courtesy URL. TypeError joins the net, so every malformed marker now degrades to the hint.

2. The root comparison was asymmetric. The trace side was .resolve()d, the marker's live_root was trusted verbatim. serve does write it resolved, but a hand-edited or symlinked spelling of the same directory failed the lexical relative_to and silently lost the URL. Both sides resolve now, and the resolve is inside the guarded block (OSError included).

3. The hint hardcoded http://127.0.0.1:8000. An operator serving on any other port got an instruction quoting a URL their own grapharc serve command does not produce. The hint now reads the marker's last-known base URL with the same tolerance (_marker_base()), falling back to the default only when there is no readable marker at all. A stale marker is exactly the case where this matters: the server is down, and the instruction should name the port the operator actually uses.

Tests

Three new, in the existing watch-line block of tests/test_cli.py:

• test_a_malformed_marker_degrades_to_the_hint_instead_of_crashing — null port and array-shaped marker both return None (both raised TypeError before).
• test_an_unresolved_marker_root_still_matches_through_a_symlink — a live listener plus a marker whose root is an unresolved symlink spelling; the URL is produced.
• test_the_hint_quotes_the_marker_port_when_the_server_is_down — dead port in the marker; the fallback watch line quotes that port, not 8000.

The existing pins (exact URL on a live server, None on a stale marker, None outside the root, no-marker instruction with the 8000 default) are untouched and green. Full suite: 1,994 passed, 12 deselected; ruff clean.

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