Add custom campaign roll composer

README.md

@@ -67,6 +67,7 @@ Gameplay capabilities now include:
 - Rolemaster create/edit forms now keep the expression authoritative, show generic Rolemaster syntax help, and reveal `FumbleRange` only when the expression is an open-ended percentile roll
 - Rolemaster roll execution now supports generic standard Rolemaster rolls (`NdS+x`, with implicit count `1` for `dS`) plus open-ended percentile (`d100!+x`) with recursive high-end chaining and low-end subtraction based on `FumbleRange`; low-end trigger rolls are shown for auditability but do not count toward the total
 - Compact campaign-log summaries stay dense for Rolemaster rolls, while lazy-loaded roll detail includes ordered die metadata for each open-ended follow-up step
+- Play screen campaign logs now include a bottom-mounted custom roll composer that records arbitrary expressions against the selected character without creating a skill; invalid expressions stay inline on the field with tooltip/error styling instead of using error toasts
 - Startup migration coverage is validated against a copied temp-file instance of `RpgRoller/App_Data/rpgroller.development.db` before feature work is considered complete
 
 ## Prerequisites
@@ -130,6 +131,7 @@ dotnet dotnet-ef migrations add <MigrationName> --project RpgRoller/RpgRoller.cs
 - Workspace campaign data is loaded in bounded slices: visible campaign summaries, a selected campaign roster, a selected character sheet, and a 25-row incremental log window backed by `/api/campaigns/{campaignId}/log/page`.
 - Campaign log rows now ship compact summary data first, including structured special-event badges for wild dice spikes, natural 1/20 results, and Rolemaster rare/fumble triggers, and lazy-load dice + breakdown detail through `/api/rolls/{rollId}` only when a row is expanded.
 - Newly appended campaign-log rolls auto-expand in the play workspace, with the roll response reused as the initial detail payload for the local roller to avoid an extra detail fetch.
+- The campaign log footer supports custom roll submission for the currently selected character; D6 custom rolls use the baseline one-wild-die/fumble behavior, while D&D 5e and Rolemaster rely only on the submitted expression.
 - Hot API contracts share a source-generated `System.Text.Json` context, and HTTP JSON responses are gzip-compressed when the client advertises support.
 - OpenAPI contract source remains at `openapi/RpgRoller.json`.