Epic — Release 0.4.3 theme follow-ups (TP-F1–TP-F4)

[ZhuchkaTriplesix]

Milestone: 0.4.3
Depends on: 0.4.2 custom theme registry (TP-01–TP-30, shipped)

Source: docs/planned-0.4.3.md, docs/theme-parser-github-issues.md (TP-F1–TP-F4).

Goal

Ship deferred theme-system follow-ups from the 0.4.2 epic: auto-discovery of filesystem changes, richer theme metadata for a future marketplace, optional visual authoring, and guarded remote install.

Child issues (suggested order)

1. TP-F1 — File watcher for user themes folder #160 — TP-F1 — File watcher for {appSupport}/themes/
2. TP-F2 — Theme marketplace metadata #161 — TP-F2 — Marketplace metadata on ThemeDefinition / manifests
3. TP-F3 — Visual theme editor in Preferences #162 — TP-F3 — Visual theme editor in Preferences (export querya.theme.v1)
4. TP-F4 — Remote theme install from URL #163 — TP-F4 — Remote theme install from URL (checksum + trust policy)

Out of scope

• Full Extensions sidebar UI and marketplace backend (likely 0.5.0, see docs/market-tech.md)
• P2 Mongo/Redis semantic token colors
• re_editor / LSP editor replacement

Release criteria

• All TP-F1–TP-F4 issues closed (or explicitly deferred with changelog note)
• flutter analyze clean, flutter test green
• CHANGELOG 0.4.3 entry drafted
• Docs updated (theme-custom-json.md, planned-0.4.3.md status)

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