W0110 inline fallback warning + docs refresh

W0110: when a function marked `inline` has a body shape the IR
lowerer can't splice (conditional early return, loops, nested
control flow, empty void body), the analyzer now emits a
warning at the declaration site so the declined hint is
visible instead of silently falling back to a regular JSR.

Implementation:
  - New `W0110` error code in `src/errors/diagnostic.rs` (warning level).
  - New `pub fn can_inline_fun(return_type, body) -> bool` in
    `src/ir/lowering.rs`, extracted from the existing capture
    logic so the analyzer and the IR lowerer share the same
    eligibility rules and can never drift.
  - New `check_inline_declinability` analyzer pass called from
    the tail of `analyze_program`, mirroring the existing
    `check_sprite_scanline_budget` / `check_unreachable_states`
    passes. Emits W0110 with help + note text pointing at the
    two accepted body shapes.
  - `capture_inline_bodies` now defers to `can_inline_fun`
    instead of duplicating the match pattern, so the two sides
    stay in lockstep by construction.

Four regression tests in `src/analyzer/tests.rs` cover the
conditional-return and while-loop declines plus the two
accepted shapes (single-return expression, void sequence).

Example source cleanups: `wrap52` in `examples/war/deck.ne`
and `abs_diff` in both `examples/arrays_and_functions.ne` and
`examples/loop_break_continue.ne` drop the `inline` keyword.
All three were dead hints — the `inline` was being silently
declined before this change, so removing it is source-only;
the three ROMs are byte-identical, all 32 emulator goldens
still match.

Docs refresh
  - `docs/language-guide.md`: rewrote the Inline Functions section
    (real behaviour + W0110), added W0105/W0106/W0107/W0108/W0109/
    W0110 to the warnings table, added the `debug.sprite_overflow*`
    builtins + sprite-per-scanline mitigations section to the
    Debug Mode docs, added a `cycle_sprites` statement entry and
    cross-referenced it from `draw`.
  - `docs/nes-reference.md`: fleshed out the "NEScript Memory
    Usage" block with the full ZP + high-RAM layout, including
    the new `$07EF` / `$07FC` / `$07FD` slots for sprite cycling
    and the debug sprite-overflow telemetry.
  - `docs/future-work.md`: documented all four debug query
    builtins in the "What ships today" block; updated the open
    "OAM allocation strategy" question to reference the shipped
    `cycle_sprites` path and ask about an automatic-flicker
    game attribute as a follow-up.
  - `docs/architecture.md`: updated the `ir/` and `optimizer/`
    module summaries to describe real inline splicing (now
    in lowering, not the optimizer).
  - `README.md`: reframed the `inline` bullet from "hint" to
    "real splicing for single-return / void-body shapes";
    expanded the debug-support bullet to mention the four
    query builtins and their stripping in release builds; added
    a new bullet for the three-layer sprite-per-scanline
    mitigations; bumped the test count from 497 → 694; updated
    the war.ne entry to mention the seven compiler bugs are all
    fixed and point readers at `git log` (instead of the
    deleted COMPILER_BUGS.md).
  - `examples/README.md`: same `git log`-pointing rewrite for
    the war.ne entry.

Deletions
  - `examples/war/COMPILER_BUGS.md` is removed. All seven
    catalogued bugs are fixed; the file's historical value
    lives in `git log` now. Every source-code comment and doc
    reference to the file has been updated to either point at
    `git log` or just describe the bug in place.

Test count: 616 unit + 75 integration + 3 doctests = 694 total.
Clippy / fmt clean. 32/32 emulator goldens match.

https://claude.ai/code/session_0143dTgh3UeRrtfHgQwzcv5z

docs/nes-reference.md

@@ -53,10 +53,23 @@ The 6502's 3-register architecture drives the compiler's register allocator. The
 ### NEScript Memory Usage
 
 The compiler reserves the following:
-- `$00`-`$0F`: System use (frame counter, temp registers, NMI flags)
-- `$10`-`$FF`: Available for `fast` variables and compiler-promoted variables
+- `$00`-`$0F`: System use (frame counter, input, OAM cursor, SFX/music pointers, mul/div scratch)
+- `$10`: `ZP_BANK_CURRENT` (current switchable PRG bank index, only in banked programs)
+- `$11`-`$17`: PPU update slots (palette/nametable flags and pending pointers, only when the program declares palette or background blocks)
+- `$18`-`$7F`: Available for `fast` variables (user zero-page)
+- `$80`-`$FF`: IR codegen temp slots (scratch for expression evaluation)
 - `$0200`-`$02FF`: OAM shadow buffer (DMA'd to PPU each frame)
-- `$0300`-`$07FF`: General variables, state-local storage
+- `$0300`-`$07EE`: General variables, per-function RAM (parameter spill + locals), state-local storage
+- `$07EF`: `SPRITE_CYCLE_ADDR` — rotating offset byte used by `cycle_sprites` (only when the program emits a `cycle_sprites` statement)
+- `$07F0`-`$07F7`: Audio channel state (noise/triangle/sfx-pitch pointers; only when the program declares a matching sfx)
+- `$07FC`: `DEBUG_SPRITE_OVERFLOW_FLAG_ADDR` — per-frame sticky bit (debug builds only)
+- `$07FD`: `DEBUG_SPRITE_OVERFLOW_COUNT_ADDR` — cumulative PPU sprite overflow counter (debug builds only)
+- `$07FE`: `DEBUG_FRAME_OVERRUN_FLAG_ADDR` — per-frame sticky bit (debug builds only)
+- `$07FF`: `DEBUG_FRAME_OVERRUN_ADDR` — cumulative frame overrun counter (debug builds only)
+
+Release-mode programs that don't opt into audio, banking, debug, or
+sprite cycling leave the corresponding slots untouched and the
+analyzer is free to allocate user globals over them.
 
 ---