Improve opening_hours placeholder clarity

[eeshm]

Description, Motivation & Context

Replaces the opening_hours field placeholder from Unknown to Mo-Fr 09:00-18:00 in data/fields/opening_hours.json.

• opening_hours uses a structured syntax, so a concrete example is clearer and helps mappers enter valid values.
• Scope is intentionally small: text-only change, no logic/UI behavior changes.

Related issues

• none

Links and data

Relevant OSM Wiki links:

• https://wiki.openstreetmap.org/wiki/Key:opening_hours

Relevant tag usage stats:

• https://taginfo.openstreetmap.org/keys/opening_hours

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### Wording

- [ ] American English
- [ ] `name`, `aliases` (if present) use Title Case
- [ ] `terms` (if present) use lower case, sorted A-Z
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[eeshm]

Test-Documentation

Preview links & Sidebar Screenshots

• Link
• Verified that the Hours field now shows placeholder Mo-Fr 09:00-18:00.

Search

• N/A (no preset/search terms changed)

Info-i

• N/A (no info-i content changed)

Wording

• American English
• name, aliases (if present) use Title Case (N/A - unchanged)
• terms (if present) use lower case, sorted A-Z (N/A - unchanged)

[1ec5]

@tyrasd, I think iD’s taginfo-based suggestions used to override this placeholder, but I no longer see them even though they appear in the dropdown menu. Instead it says “Unknown…” based on the placeholder property. Could it be fallout from openstreetmap/iD#11794? This PR would address this one instance, but others like service_times=* would still be affected.

[matkoniecz]

Currently placeholders are a wild mix

I see example values, explanations, marking values as unknown if unset.

Not sure which is best. Do we have documented anywhere for what placeholders are supposed to be?
I guess that optimal form will depend on case but it seem a bit too much.

[eeshm]

thanks, this makes sense.

I agree this PR likely addresses only one instance. My goal here is a narrow improvement to opening_hours, where Unknown is less helpful than a valid example for a very common field.

I also agree there’s a broader consistency question for placeholders (example vs explanation vs unknown-state wording), and possibly an iD-side behavior change in how suggestions/placeholder are shown.

If this scope is acceptable, I’d like to keep this PR limited to opening_hours and open a follow-up issue for:

1. placeholder style guidance in id-tagging-schema
2. whether iD placeholder/suggestion behavior changed (possibly related to fixes rare tag value auto suggestions (fix #11782) iD#11794)