docs(user): T2 modifier profile features

- Hot-Swap rewritten for solo vs multiplayer: propose/consent with
  60s window, turn-boundary semantics, last-write-wins on rapid
  proposals. Drops the T1 host-only caveat.
- New Editor Features section: undo/redo (Cmd/Ctrl+Z, 50-deep,
  cleared on save/cancel), per-instance and per-type copy/paste
  (editor-local clipboard), conflict resolution panel with Fix
  buttons plus the manual-only cases.
- New Board Indicators section: fuchsia dot on modified pieces,
  updates across hot-swaps.
- In-Play Inspection expanded with the enhanced source chain
  (per-instance / per-type / preset / default) and the combine
  semantics (HP additive, resistance multiplicative, directions
  unioned).
- Known Limitations: drop the T1 host-only bullet; add a Coming
  in T3 subsection (custom authoring, auras, multi-profile
  stacking).

docs/user/modifier-profiles.md

@@ -92,14 +92,65 @@ Values: 0 (no resistance) to 1 (full immunity).
 
 ---
 
+## Editor Features
+
+### Undo / Redo
+
+- **Cmd/Ctrl+Z** to undo, **Cmd/Ctrl+Shift+Z** to redo.
+- Toolbar buttons in the editor header (↶ / ↷) with the same behaviour.
+- History is capped at 50 actions per editing session.
+- The stack is cleared when you **Save** or **Cancel** — the saved state
+  becomes the new baseline, so there is no undo across sessions.
+
+### Copy / Paste
+
+- **Per-instance**: select a square that already has modifiers, click **Copy**,
+  then select another square and click **Paste**. Pasted modifiers replace any
+  same-kind modifier already present on the target (so you won't end up with
+  two HP-Bonus entries on the same piece).
+- **Per-type**: each row has a **Copy** button. Use **Paste** at the top of the
+  panel to apply the copied entry to a different piece type / color.
+- The clipboard is editor-local (in-memory) and does **not** use your OS
+  clipboard — copying modifiers cannot clobber anything you already copied
+  outside the app.
+
+### Conflict Resolution
+
+When the editor detects a problem — a king carrying the `CANNOT_BE_CAPTURED`
+flag, a per-instance entry pointing at an empty square, an attribute-limit
+overflow — a panel appears at the top of the editor listing every issue.
+
+- Each issue has a **Fix** button that auto-resolves it where possible
+  (e.g. drop the illegal flag, remove the orphan entry).
+- Some issues (missing kings for a layout, attribute-limit overflow that
+  requires a real decision) can't be fixed automatically; the Fix button is
+  advisory and the panel directs you to the specific row that needs manual
+  attention.
+- Save is blocked while any hard error remains; warnings (orphan per-instance
+  entries) don't block save but surface in the panel so they aren't silently
+  ignored.
+
+---
+
 ## Hot-Swap
 
-Profiles can be changed mid-game by the host (creator of the room). Click the
-rules drawer while in a game and select a new profile. Changes take effect after
-the current interaction.
+Modifier profiles can be changed mid-game. The flow:
 
-*Note*: Two-player consent model is planned for T2. In T1, the host can change
-profiles unilaterally.
+1. **Solo mode**: Open the editor, change the profile, save. The new profile
+   applies after the next move.
+2. **Multiplayer**: Either player can propose a profile change. The opponent
+   receives a notification with a 60-second window to approve or reject. If
+   approved, the new profile applies after the next move; if rejected or timed
+   out, no change occurs.
+
+Profile changes always take effect at a **turn boundary** (after the next
+completed move), never mid-move. This guarantees both players' moves resolve
+under the same rule set they were planned with — the state at turn N is fully
+determined by the profile active at turn N plus moves 1..N.
+
+In a multiplayer room, rapid successive proposals follow a last-write-wins
+rule: if you propose a swap and then send a second proposal before the opponent
+decides, the first is superseded and the opponent sees the new candidate.
 
 ---
 
@@ -117,16 +168,50 @@ profiles unilaterally.
 
 **Hover** any piece on the board to see a tooltip listing active modifiers.
 
-**Click** a piece to pin a side panel with the full modifier breakdown, including
-the source of each modifier (per-type, per-instance, or from an active preset).
-The panel stays pinned across turns until you dismiss it (×) or click another piece.
+**Click** a piece to pin a side panel with the full modifier breakdown. The
+panel stays pinned across turns until you dismiss it (×) or click another
+piece.
+
+The pinned panel shows the **source** of each modifier so you can trace where
+a value comes from at a glance:
+
+- **per-instance: {square}** — attached to this specific board position
+  (survives captures of other pieces, but vanishes if this piece is captured).
+- **per-type: all {color} {type}s** — applies to every piece matching this
+  type + color combination.
+- **from {preset name}** — the modifier comes from an active rule preset
+  (e.g. a first-blood ruleset granting kings extra HP).
+- **default** — the engine's baseline value with no modifier applied.
+
+When multiple sources touch the same attribute, the panel lists each source
+and shows how they combine (HP additive, damage-resistance multiplicative,
+direction-additions unioned).
 
 ---
 
-## Known Limitations (T1)
+## Board Indicators
+
+Pieces with one or more active modifiers display a small **fuchsia dot** in
+the top-right corner of their square. The dot is visible without hover, so
+you can tell at a glance which pieces are running on modified rules.
+
+- Hover the piece to see a tooltip with modifier details.
+- Click to pin the inspection panel (see above).
+- The dot stays visible across moves and updates live when a profile is
+  hot-swapped at the next turn boundary.
+
+---
+
+## Known Limitations
 
-- Only the host can swap profiles mid-game. Two-player consent coming in T2.
 - Maximum 20 profiles in the local library per browser.
 - Profiles larger than 8 KB cannot be URL-shared.
 - CANNOT_BE_CAPTURED cannot be applied to kings.
 - Deadlock detection (all legal moves blocked) not yet implemented.
+
+### Coming in T3
+
+- Custom modifier authoring (defining new modifier categories from scratch).
+- Cross-piece aura effects (e.g. "all pieces within 2 squares of this priest
+  get +1 HP").
+- Multi-profile stacking (combining two profiles in one game).