Merge main into feat/v0.8.8-tui-polish + gemini-code-assist feedback

Resolves the post-#514/#517/#518 conflicts:

- CHANGELOG.md: kept both polish-stack and Linux ARM64 entries under
  [Unreleased]; reordered so the ARM64/install-message Changed/Docs
  sections precede the Releases footer.
- config.example.toml: kept both the `instructions = [...]` example
  and the `[memory]` opt-in stanza in sequence.
- crates/tui/src/config.rs: kept both `instructions_paths()` (#454)
  and `memory_enabled()` (#489) on the Config impl.
- crates/tui/src/prompts.rs: extended
  `system_prompt_for_mode_with_context_and_skills` to take BOTH
  `instructions: Option<&[PathBuf]>` and `user_memory_block:
  Option<&str>`. Section 2.5a renders instructions; 2.5b renders the
  memory block — both above the skills block so KV prefix caching
  still wins.
- crates/tui/src/core/engine.rs: thread both args through the two
  call sites.
- crates/tui/src/prompts.rs: update the `system_prompt_for_mode_with_context`
  forwarder and the test caller to pass `None` for the new arg.
- .gitignore: ignore `.claude/*.local.md` and `*.local.json` so
  local ralph / Claude-Code notes can't leak into commits.

Folds in two valid suggestions from the gemini-code-assist review on #519:

- `client.rs`: collapse the duplicated `LlmError → label` match and the
  `human_retry_reason` body into a single
  `retry_reason_label_and_human(err) -> (&'static str, String)` helper.
- `widgets/footer.rs::retry_banner_spans`: merge the two separate
  `match &props.retry` blocks into one that returns both `(label, color)`.

Behavior is unchanged; refactor is a pure DRY win.

.gitignore

@@ -74,3 +74,7 @@ apps/
 .claude/worktrees/
 .worktrees/
 .ace-tool/
+
+# Local-only Claude / ralph notes
+.claude/*.local.md
+.claude/*.local.json