megacommit:

- setup new UI layout using tiling and an action/message based system for updating global state based on interactions with individual tiles and vice versa
- added custom dialogs and UI helpers to create a more cohesive UI
- added a disassembler widget (WIP)
- added a documentation widget (WIP)
- refactored backend halt/pause logic to fix bugs.
- started emulator implementation documentation (to complement the ISA spec)

doc/DSA State Machine Semantics.md

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+# States
+
+### Definitions
+- Model
+  - Private - internal state of the processor, always up to date.
+    - time: Duration, 
+    - state: **Running | Paused | Halted | Shutdown | Breakpoint**
+  - Shared - shared across threads. updated periodically
+    - time: Duration
+    - cycles: Integer
+
+
+## Running
+the running state is the main loop of the emulator. 
+
+### Responsibilities:
+- run fetch-decode-execute cycle
+- handle interrupts
+- go to paused state if requested by UI.
+- go to the halted state if it hits that instruction
+- keep the UI updated occasionally, but prioritise extremely high throughput
+
+### Transitions:
+- to `Paused`
+  - when the `pause` signal is received
+- to `Halted`
+  - when hitting the `Hlt` instruction.
+- to `Shutdown`
+    - when the `shutdown` signal is received
+
+***DEBUG IMPLEMENTATION ONLY***
+- to `Breakpoint`
+  - when hitting a breakpoint 
+
+## Paused
+the paused state is started and ended by the UI thread.
+
+### Responsibilities:
+- update the UI when requested
+- reset when requested by the UI
+- save the running-time and executed instructions since the last pause state.
+  - add `private.time` to `shared.time`
+  - reset `private.time, shared.time, shared.cycles` on state exit
+
+### Transitions
+- to `Halted`
+  - when the `run` signal is received and the previous state was `Halted`
+- to `Running`
+  - when the `run` signal is received
+- to `Shutdown`
+    - when the `shutdown` signal is received
+
+## Halted
+the state reached when the emulator has hit a `Hlt` instruction and is waiting to continue
+
+### Responsibilities:
+- update the UI when requested
+- unpause when an interrupt is received
+- keep track of the time spent in the running state across multiple hlt/interrupt cycles
+  - add `private.time` to `shared.time`
+  - reset `private.time` on state exit
+  - preserve `shared` on state exit
+
+### Transitions
+- to `Running` 
+  - when the `interrupt` signal is received
+- to `Paused`
+  - when the `pause` signal is received
+- to `Shutdown`
+  - when the `shutdown` signal is received
+
+## Shutdown
+the shutdown state is a terminal state. the emulator cleans up its memory and exits.
+
+## Breakpoint
+debug state used only in the debugger implementation of the emulator
+
+### Transitions
+- to `Running`
+  - when the `run` signal is received