[Menelion]

What and why

PlanCake opens .md and .markdown files, but Windows did not know it: the installer registered nothing, so PlanCake was missing from Explorer's Open with list and from Windows Settings → Default apps, and a double-click on a plan never reached it.

Since Windows 10 no program can make itself the default for a file type, so the change has two halves:

• The installer always registers PlanCake as a handler for both extensions, with no checkbox: the file type PlanCake.Markdown, PlanCake in each extension's OpenWithProgids, an Applications\plancake.exe entry, and capabilities listed under RegisteredApplications. It never writes the extensions' default value, so the program the user chose keeps opening Markdown files, and the ProgID has no verb but open (File → Open in editor relies on that). ChangesAssociations=yes refreshes Explorer. The uninstaller removes PlanCake's own keys whole and only its values from the shared keys (uninsdeletevalue, uninsdeletekeyifempty).
• Settings → Advanced gets a button, "Choose PlanCake for Markdown files in Windows Settings...", with a wrapping label above it. It opens ms-settings:defaultapps?registeredAppMachine=PlanCake, PlanCake's own page in Default apps (the general Default apps page on older Windows). The button and label show only when the registration is there and PlanCake is not portable.

The plan is docs/plans/completed/002-markdown-association.md. This ships in 1.1, which waits for it.

Tasks completed

• Add the Default apps link and the button's visibility rule (Utils/DefaultApps.cs)
• Register PlanCake for .md and .markdown in the installer, with MarkdownFileType in all six .isl files
• Add the Default apps button to Settings → Advanced
• Translate the new interface strings and add the Windows terms (Default apps, Windows Settings, Open with, Choose another app, and the Windows 10 Set defaults by app and Manage) to the glossaries
• Update the six manuals: Installing, Opening a file, Uninstalling, Settings → Advanced
• Update CHANGELOG, README and CLAUDE.md

Review

• Round 1, a full sweep through seven lenses (quality, implementation, testing, simplification, documentation, conventions, accessibility): 17 findings, 12 confirmed and fixed in one commit, 5 refuted.
  • Fixed: the button was renamed so a screen reader hears where it goes (the label above it is not read when tabbing to the button); two installer tests that could pass vacuously or checked too little; the registry read failure now logs at Warning; the manuals give the Windows 10 steps; the Hebrew label and manual now agree; the installer builds its registry paths from its company and app defines; small test cleanups.
  • Refuted: more tests for IsRegistered and the dialog wiring (the plan asks for exactly the no-throw test, and the visibility rule is a tested pure function); a {cm:} cross-check (ISCC already fails on an unknown name); the visibility helper as over-engineering (the plan asks for it); a README "Open a file" gap (Installing covers it).
• Round 2, a critical re-check (quality, implementation): no findings. Every lens reported.
• Checked and found fine across the lenses: the registry lines, quoting and uninstall order; the 64-bit view the installer writes and the app reads; single-instance activation on a double-click; Open in editor falling back to Notepad when PlanCake is the default; exception handling and disposal in DefaultApps; mnemonics in all six languages; TableLayoutPanel, WrappingLabel and tab order; the manuals' ids and links.
• Codex review (gpt-6-astra, read-only, over master...HEAD): no actionable issues found.

Validation

All passed on the final commit:

• ./src/PlanCake/locale/scripts/Compile-Translations.ps1 -Strict (no fuzzy entries)
• dotnet build
• dotnet test (1286 tests)
• dotnet format --verify-no-changes
• ./installer/Build-Installer.ps1 -AllowDirty (the installer compiles; it was not run)

FileWatcherTests.Polling_ReadsTheFileOnlyWhenItsSizeOrTimeChanged and Polling_LooksAtTheFileEverySecond_AndReportsAChange failed now and then and passed on a rerun. They come from the WSL polling change, not this one, but they are flaky enough to need their own fix.

To check by hand

• Installer, on a machine where another program already opens .md:

  • install, and check the default did not change;
  • check that PlanCake is in Open with for both extensions and in Default apps with its icon;
  • set it as the default there, double-click a plan whose path has spaces, and double-click it again while it is open (its window comes forward);
  • uninstall, and check that the PlanCake keys and the RegisteredApplications value are gone, that OpenWithProgids lost only PlanCake's value, and that the other program still opens .md.

  Repeat on Windows 10 if one is at hand.

• JAWS, in Settings → Advanced:

  • the label and the button read well;
  • the button opens PlanCake's page in Default apps, which works from the keyboard;
  • the button is absent in the portable build.

  Check the Hebrew interface too.

• Windows 10 terms: the Ukrainian and Hebrew names for "Set defaults by app" and "Manage" in the manuals and glossaries were not checked against a localized Windows 10.