Add data set favorites: f to toggle, favorites popup with notes, wildcard favorites

[Tannex]

Implements #16. Stacked on PR #23 (issue-15-dsn-copybook-mappings) — merge that first; this PR reuses its internal/dsnmap wildcard matcher and state-file conventions.

What's here

• internal/favorites: JSON state store at <config>/cq/favorites.json (pattern, optional note, created/lastUsed). Same graceful degradation as dsnmap: missing file = empty store, corrupt file = read-only (never overwritten), unknown JSON fields tolerated. Wildcards use the shared cq dialect via dsnmap.MatchPattern (* any run, % exactly one char) — no new dialect.
• f on the data set list toggles the selected data set as an exact favorite. A dedicated 1-char star column (★) marks rows that are favorited exactly or covered by a wildcard favorite; f on a wildcard-covered row favorites the exact DSN and never mutates the wildcard entry (status notes when a removed exact entry is still wildcard-covered).
• F opens the favorites popup, composited over the live view with the same lipgloss Canvas/Layer mechanism and tiny-terminal full-area fallback as the help popup. Entries list in most-recently-used order with notes; enter jumps (the favorite pattern becomes the data set prefix filter and fetches — exact favorites list/select that one data set), n edits the note inline (single-line input; enter saves, esc cancels), x removes, esc/F closes.
• Bindings surfaced in short help and the help popup; mouse wheel moves the popup selection; cmd/cqt wires favorites.DefaultStore (demo mode included, matching how Persist DSN → copybook mappings (JSON state, wildcard DSN patterns, dialog integration) #15 wires the mapping store).

Decisions on the issue's open questions

• Popup binding: F, data set screen only (favorites act on the data set list, so that is where the popup lives).
• Ordering: most-recently-used (jump Touches the entry), lexicographic tie-break.
• Note editing: inline single-line input in the popup, not a separate dialog.
• Scope: global store (matches the Persist DSN → copybook mappings (JSON state, wildcard DSN patterns, dialog integration) #15 decision for dsn-copybooks.json); per-profile scoping can be layered on later if profile collisions bite in practice.

Tests

• internal/favorites: toggle add/remove, wildcard match without mutation, persistence round-trip incl. unknown fields, MRU ordering, corrupt-file read-only degradation, missing file, note validation.
• internal/cqt: toggle + star marker, wildcard marking with exact-DSN toggle, popup jump (prefix + fetch + touch), navigation/remove/clamping, note editing (keys route to the input while editing), nil-store degradation, empty-popup state.
• go build ./... && go vet ./... && go test ./... all pass; existing suite untouched.

Closes #16

🤖 Generated with Claude Code

[Tannex]

Follow-up: the shared pattern dialect now also accepts /regex/ patterns (see PR #23's second commit). A commit on this branch keeps regex favorites intact — normalization preserves case so classes like \d survive, regex entries count as pattern favorites for row marking, and invalid regexes are skipped with a diagnostic on load. Note: jumping to a regex favorite applies it as the dataset prefix filter, which the z/OSMF list API cannot interpret — regex favorites are mainly useful for row marking and notes.