Snap: a new caption replaces 'Your text', a stray comma never blocks Save, and the editor and page say what they do

The issue bundles five separate changes, so pick one to start. The smallest is item 2: trim and drop empty tags in SnapModel.saveDraft (SnapModel.swift around lines 515-538) and check it against SnapItem.validate in SnapStore.swift. Done when the two checks in ImageWorkspaceChecks pass under --check-image-workspace: ["pricing", ""] saves as ["pricing"] and [""] saves as [].

Outcome: a new text box is ready to type over. A trailing comma in Tags never stops a Snap from saving. The Pen, Arrow and Box slider says it is the line width. Search says it reads the text in images. A tagged Snap no longer pushes its row's actions out of line.

1. Typing into a new caption replaces 'Your text'

Evidence (train head 14d06bc)

• Text runs editing.addText(); textFocused = true (SnapEditorView.swift:34). addText creates 'Your text', selects it and sets tool = .select (ImageWorkspaceEditing.swift:148-151).
• The caption is a plain TextEditor (SnapEditorView.swift:94-96), and nothing selects its text. NSTextView does not select its text when it takes focus.
• The TextEditor is not mounted until that same closure selects the mark, so focus may not land at all. If the canvas keeps focus, Delete removes the whole box (ImageWorkspaceCanvas.swift:225).
• So every caption starts by clearing the placeholder. Preview and Keynote select theirs.
• ImageWorkspaceCanvas.swift:159 handles editing.tool == .text, but nothing ever sets the tool to .text (only .select and .crop), so that branch is unreachable.

Change

• The Text button raises a one-shot caption focus request, set by a new method the button calls. It is not set by addText(), which SurfaceGallery.swift:2860 and the checks call directly.
• On that request, the inspector makes the caption's NSTextView first responder and selects all of it, through a narrow AppKit hook beside the TextEditor.
• Only if that hook can't be made reliable, use a minimal NSTextView representable. It must keep the 'Text on image' label, the body font, the 10,000-character cap, the end of the edit run on blur (SnapEditorView.swift:96) and ⌘Z going to the editor's Undo.
• Cover both the first box and Text pressed while a caption already has focus.
• Delete the unreachable branch at :159, keeping the .text case.
• Undo coalescing is unchanged: one Undo returns 'Your text'.

Acceptance (--check-image-workspace)

• After calling the button's method, panel.firstResponder is an NSTextView labelled 'Text on image' with selected range (0, 9).
• insertText("Login", replacementRange:) gives selectedMark.text == "Login", and one Undo returns 'Your text'.
• The same holds when a caption already has focus.
• These fail on 14d06bc. The existing undo-run checks (ImageWorkspaceChecks.swift:299-336) and the editor renders are unchanged.

2. A trailing comma or a cleared Tags field never blocks Save

Evidence

• The Tags field (SnapEditorView.swift:129-131) splits on commas without dropping empty pieces.
  • 'pricing,' stores ["pricing", ""].
  • Typing in the field and then clearing it stores [""], while the field looks empty.
• SnapItem.validate requires every tag to be non-empty (SnapStore.swift:100). Otherwise it throws 'This Snap record is not supported or is damaged. Its files have been kept.' (:105). Both insert and save validate (:188, :205).
• saveDraft reports 'Snap was not saved. …' (SnapModel.swift:538). The draft survives, but the reason given is false and nothing points at the comma.

Change

• In SnapModel.saveDraft (:515-538), trim the tags and drop empty ones before insert or save (:522, :527).
• Do not do this in the field's binding, which would swallow a comma while it is being typed.

Acceptance

• A check where a SnapModel is available, such as ImageWorkspaceChecks:
  • a draft with ["pricing", ""] saves with ["pricing"];
  • a draft with [""] saves with [].
• Both fail on 14d06bc.

3. The Pen, Arrow and Box slider says Line width

Evidence

• The selected-mark slider (SnapEditorView.swift:110-111) and the tool-chosen slider (:119) have only a VoiceOver label. Text size has a visible caption with its value (:102-106).
• With Pen chosen, the slider changes nothing visible until the next mark (ImageWorkspaceEditing.swift:84, ImageWorkspaceCanvas.swift:207), and drawing a mark does not select it (:212-214).
• No editor render shows either branch.

Change

• Put a 'Line width · N px' caption above both sliders, where N = Int(max(1, width × min(imageSize.width, imageSize.height))). This is the width SnapRendering draws (SnapRendering.swift:113).
• Keep the VoiceOver labels and updateSelected("width").

Acceptance

• An editor render with an arrow selected, in light and dark, shows 'Line width · 13 px' for width 0.006 on the 2,880×1,800 fixture.
• The other editor renders are unchanged.

4. Search says it reads the text in images

Evidence

• Search matches the image text Vision reads (SnapModel.swift:147-154), as docs/snap.md:43 and HistoryChecks (:80) say.
• But the field reads 'Search titles, notes and tags' (SnapWorkspaceView.swift:66). An empty result says 'Try another title, note or tag.' (:152). The handbook says the same (site/handbook/contract.json:26).

Change

• Placeholder: 'Search titles, notes, tags and image text'.
• Empty result: 'Try another title, note, tag or words shown in the image. Your selection is kept.'
• Update the handbook sentence to match.

Acceptance

• The placeholder shows in full at 1180 pt and at 1050 pt.
• HistoryChecks, scripts/test-snap.sh and the site's handbook tests pass.
• No 'notes and tags' is left in Sources or site.

5. A tagged Snap keeps its actions level with its row

Evidence

• Titles reserve two lines so the cards align (SnapWorkspaceView.swift:209).
• The tag line appears only when tags exist (:212), and the grid aligns cards to the top (:100).
• In tonight's page-snap renders, the tagged card's bottom edge and Copy row sit about 20 pt below its neighbours'.

Change

• When any visible Snap has tags, hold the tag line on every card with .lineLimit(1, reservesSpace: true), hidden from VoiceOver when empty.
• Grids with no tags are unchanged.

Acceptance

• In page-snap default and narrow renders, light and dark, the cards in a row share one bottom edge and one Copy row within 1 px.

Value before scope

1. Outcome: fewer steps on every caption, and no Save blocked behind a false 'damaged' message. Evidence above.
2. Simpler route: platform behaviour (select the placeholder), normalising tags at save, and copy changes.
3. Owner: the Snap editor, SnapModel.saveDraft and the Snap page.
4. Complexity: small. One unreachable branch is removed.
5. Verified by: --check-image-workspace, editor and page renders, and site tests.

Grammar: Quality.

Refs #112

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Build-ready record from the 15 Oct round-three pass (delight and code-base value), verified against the release train head 14d06bc by an independent skeptic per item. Closes only after native acceptance.