Let rules carry a note

A glob like *4412* says nothing about why it exists or who it catches, and
six months later neither does memory. Rules get an optional note: free text
that never takes part in matching, written as a TOML key rather than a
comment so it survives a round trip and can be shown back.

The rule builder grows a fourth field for it and the rules screen a last
column. Four fields spaced out are taller than a short window has room for,
so the form now drops its blank lines and then the hints on unfocused fields
before anything would run off the bottom.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -100,14 +100,22 @@ a `▸` against each one the glob currently matches and a running
 ╰────────────────────────────╯
   tab completes · ctrl+n: 1 more
 
+  note
+╭────────────────────────────╮
+│ optional                   │
+╰────────────────────────────╯
+  why this rule exists
+
   2 of 7 descriptions match
 ```
 
 Only `gro` was typed in the tag field; `ceries` is the ghosted completion.
 
-`tab` / `↑↓` move between the glob, account and tag fields, `pgup` / `pgdn`
-scroll the list, and `enter` appends the rule to `rules.toml` and retags
+`tab` / `↑↓` move between the glob, account, tag and note fields, `pgup` /
+`pgdn` scroll the list, and `enter` appends the rule to `rules.toml` and retags
 immediately, so the rows it caught disappear from the list. `esc` goes back.
+On a short window the form gives up its spacing and then its hints, so all four
+fields stay on screen.
 
 The account and tag fields complete as you type: the rest of the match is
 ghosted in grey after the cursor, and `tab` (or `→` at the end of the line)
@@ -131,12 +139,12 @@ Rules that claim none are marked `✗`.
 ```
 money · rules · 5 rules · 2 match nothing
 
-#      Pattern                Account     Tag         T  Txns
-1      *LIDL*                 (all)       groceries      3
+#      Pattern                Account     Tag         T  Txns  Note
+1      *LIDL*                 (all)       groceries      3     the weekly shop
 2   ✗  *LIDL SOFIA*           (all)       shadowed       0
-3   ✗  *OLD BANK NAME*        (all)       dead           0
+3   ✗  *OLD BANK NAME*        (all)       dead           0     closed in 2025
 4      *ZARA*                 (all)       clothes        1
-5      *КАУФЛАНД*             checking    groceries      1
+5      *КАУФЛАНД*             checking    groceries      1     4412 is the branch
 ```
 
 The count is how many transactions the rule *wins*, not how many its glob could
@@ -161,6 +169,12 @@ A rule matches on `match` (the description), `counterparty` (the other side's
 account number) and `type` (the bank's own classification). Setting several is
 an "and": all must match.
 
+`note` is free text for you, never for the matcher: why the rule is there, or
+what the unrecognisable payee behind the glob actually is. It shows in the last
+column of the rules screen. Ordinary `#` comments still work and are preserved
+on delete; a `note` differs in that it survives a round trip through the tool,
+so the rule builder can write one and the rules screen can show it.
+
 ```toml
 [[rule]]
 tag   = "groceries"
@@ -169,6 +183,7 @@ match = "*LIDL*"
 [[rule]]
 tag   = "salary"
 match = "*ACME PAYROLL*"
+note  = "paid on the 4th; the December one lands early"
 
 # Money moved between your own accounts. Both legs need a rule.
 [[rule]]