docs: update CHANGELOG and README for development changes

Assisted-by: MiMo V2.5 Pro

CHANGELOG.md

@@ -11,7 +11,44 @@ Unreleased changes on the `development` branch.
 
 ### Added
 
--
+- **Multi-architecture debugger.**  `gasm debug` works on arm64, riscv64
+  and loong64 in addition to amd64.  Each architecture has its own ptrace
+  register access, disassembler (`golang.org/x/arch`), register display,
+  and stop-info handler.  The REPL is fully arch-neutral.
+- **JIT execution trampolines.**  `verify.Call` now works on all four
+  architectures via hand-written assembly trampolines
+  (`trampoline_{arm64,riscv64,loong64}.s`) that save the Go stack, switch
+  to a prepared stack, and branch to the JIT function.
+- **Hardware watchpoints on all architectures.**  arm64 uses DBGWVR/DBGWCR
+  via `PTRACE_SETREGSET` with `NT_ARM_HW_BREAK`; riscv64 and loong64 use
+  `PTRACE_POKEUSER` to access trigger/debug registers.
+- **LSP: find references** (`textDocument/references`).
+- **LSP: rename symbol** (`textDocument/rename`).
+- **LSP: document formatting** (`textDocument/formatting`) using the
+  `format` package for canonical gofmt-style output.
+- **LSP: inlay hints** (`textDocument/inlayHint`) — frame size hints after
+  the TEXT directive's argument area.
+- **Lint: `unused-label` rule.**  Flags labels that are defined but never
+  referenced by any jump (Hint severity).
+- **Lint: `invalid-textflag` rule.**  Flags TEXT/GLOBL flags not in the
+  known set from `textflag.h` (Warning severity).
+- **Lint: `stack-imbalance` rule.**  Tracks SP changes and flags if the
+  net delta at RET does not match the declared frame size.
+- **DWARF5 debug sections in ELF output.**  All four ELF emitters now emit
+  `.debug_abbrev`, `.debug_info`, `.debug_line`, and `.debug_line_str`
+  sections, enabling `addr2line` and GDB/LLDB source-level debugging.
+
+### Fixed
+
+- **arm64 BL relocation.**  `BL sym(SB)` now records a `RelArm64Branch`
+  relocation instead of emitting a bare instruction with no relocation.
+- **GOOBJ R_ADDRARM64 constant.**  Corrected from 9 (`R_CALLARM64`) to 3
+  (`R_ADDRARM64`).
+- **Cross-package GOOBJ resolution.**  `AssembleFileRISCV`,
+  `AssembleFileLOONG64`, and `AssembleFileARM64` now mark external
+  relocations and populate `img.Externals`, enabling cross-package symbol
+  resolution in GOOBJ output.
+- **asm help text.**  Updated to list arm64 as a supported architecture.
 
 ## [0.31.1] — 2026-08-20