Enable anonymous downloads on the host and harden Strings.fmt

Host (applied with root@192.168.88.30)
- [service] REQUIRE_SIGNIN_VIEW = false in /etc/gitea/app.ini (backup written
  alongside), Gitea restarted. Verified anonymously: repo page 200, API 200, and a
  release asset downloads at full size (50.8 MB AppImage).

Localization safety (Open Polish)
- Strings.placeholder_count() counts conversions and ignores %% escapes.
- Strings.fmt() validates the count and fails safe (warns, returns the template)
  instead of raising an engine error when a key's placeholders drift.
- Strings.validate() lints the table for a trailing %, unsupported conversions, and
  mixed positional/sequential placeholders.
- Tests cover the counter, the fail-safe path, a clean table, and a formatting pass
  over every placeholder key with type-correct arguments.

Docs
- TODO: distribution, release-pipeline, and open-polish sections are complete and
  moved to DONE; the v0.2.4-v0.2.8 backfill is closed as superseded.
- README/MEMORY updated. Version 0.2.14.

src/core/strings.gd

@@ -34,12 +34,69 @@ static func lookup(key: String) -> String:
 	_ensure_loaded()
 	return TABLE.get(key, key)
 
+## Number of `%` conversion placeholders in a template, ignoring `%%` escapes.
+static func placeholder_count(template: String) -> int:
+	var count := 0
+	var i := 0
+	while i < template.length():
+		if template[i] == "%":
+			if i + 1 < template.length() and template[i + 1] == "%":
+				i += 2
+				continue
+			count += 1
+		i += 1
+	return count
+
 ## Format a string by key with positional arguments.
+##
+## GDScript's `%` binds arguments by order, so a key whose placeholder count drifts
+## from its call site would push an engine error. Validate first and fail safe: log
+## a warning and return the raw template instead of crashing.
 static func fmt(key: String, args: Array) -> String:
 	var template := lookup(key)
 	if template == key:
 		return template
+	var needed := placeholder_count(template)
+	if needed != args.size():
+		push_warning("Strings.fmt(%s): template needs %d args, got %d" % [key, needed, args.size()])
+		return template
 	return template % args
 
+## Lint the loaded table for formatting hazards. Returns an array of problems.
+## Checks: trailing `%`, invalid conversions, and mixed positional (`%1$s`) and
+## sequential placeholders in one template.
+static func validate() -> Array[String]:
+	_ensure_loaded()
+	var problems: Array[String] = []
+	for key in TABLE.keys():
+		var template := str(TABLE[key])
+		var positional := template.contains("$")
+		var sequential := 0
+		var i := 0
+		while i < template.length():
+			if template[i] != "%":
+				i += 1
+				continue
+			if i + 1 >= template.length():
+				problems.append("%s: trailing %% escape" % key)
+				break
+			var next := template[i + 1]
+			if next == "%":
+				i += 2
+				continue
+			var j := i + 1
+			while j < template.length() and template[j] in "0123456789.$":
+				if template[j] == "$":
+					positional = true
+				j += 1
+			if j >= template.length() or not (template[j] in "sdfxXv"):
+				problems.append("%s: unsupported conversion near '%%%s'" % [key, template.substr(i + 1, 3)])
+			elif not positional:
+				sequential += 1
+			i = j + 1
+		if positional and sequential > 0:
+			problems.append("%s: mixes positional (%%1$s) and sequential (%%s) placeholders" % key)
+	return problems
+
 func _init() -> void:
 	push_error("Strings is a static utility class; use Strings.lookup / Strings.fmt.")