vault: a sealed folder stays sealed

`:encrypt` on a folder sealed the files in it once; whatever arrived
afterwards was plaintext. A folder or space that is encrypted now
carries `sealed` (0015), and so does every folder under it, so "is
this place sealed?" is one column of the parent. What lands there is
sealed on the way in, or refused with 423 while the vault is shut:

- uploads, with or without `?encrypt`, encrypted as they stream
- imports, sealed where they lie before any row names them
- SFTP writes, sealed out of their `.part`, and refused at the open
  when the vault is shut
- files and folders moved in, through the web or SFTP: seal::enter
  seals them first and the move happens only if that worked

Triggers make it hold for any path: a folder made inside a sealed one
is sealed, and a file node whose media is not encrypted cannot be
inserted into or moved into a sealed folder (a 400, not a 500).
Decrypting the sealed folder lifts the flag on its subtree and opens
its files; a file or folder inside it cannot be decrypted on its own.
An empty folder can be sealed. Documents are not files and stay as
they are.

The list shows a lock on sealed folders, the touch menu offers to
unseal one, and an upload or import into one asks for the vault
password first. Tests cover sealing, inheritance, the trigger, moves
with the vault open and shut, unsealing, an SFTP write and an import.

web/src/lib/commands.ts

@@ -75,12 +75,16 @@ const sealTarget = (encrypt: boolean) =>
     if (node.file && node.file.encrypted === encrypt) {
       return workspace.say(encrypt ? 'already in the vault' : 'not in the vault')
     }
+    if (!encrypt && workspace.parentSealed) {
+      return workspace.say(`this ${node.kind} is inside a sealed folder — decrypt that folder instead`, 'error')
+    }
+    const name = node.name || node.slug
     if (isContainer(node)) {
-      const verb = encrypt ? 'seal every file in' : 'take every file in'
-      const tail = encrypt ? 'into the vault' : 'out of the vault'
-      if (!(await workspace.ask(`${verb} ${node.kind} "${node.name || node.slug}" ${tail}?`))) return
+      const question = encrypt
+        ? `seal ${node.kind} "${name}" — every file in it now, and every file added later? documents stay readable`
+        : `unseal ${node.kind} "${name}" and take every file in it out of the vault?`
+      if (!(await workspace.ask(question))) return
     } else if (!encrypt) {
-      const name = node.name || node.slug
       if (!(await workspace.ask(`store "${name}" unencrypted again, and in the readable files/ view on proton drive?`))) return
     }
     if (!(await workspace.ensureUnlocked())) return
@@ -865,14 +869,14 @@ export const commands: CommandSpec[] = [
     name: 'encrypt',
     aliases: ['seal'],
     group: 'vault',
-    help: 'seal the file under the cursor in the vault — on a folder, every file inside it',
+    help: 'seal the file under the cursor in the vault — a folder stays sealed: every file in it, and every file added later',
     run: () => sealTarget(true),
   },
   {
     name: 'decrypt',
     aliases: ['unseal'],
     group: 'vault',
-    help: 'take the file under the cursor back out of the vault — on a folder, every file inside it',
+    help: 'take the file under the cursor back out of the vault — on a sealed folder, unseal it and every file inside',
     run: () => sealTarget(false),
   },
   {