Add regression test coverage for merged PRs #13-#20 - #21

Follow-up to PR #111. Tier-2 items from the 23-bug audit batch:
docs corrections and two small correctness/UX fixes.

## Docs

- **#12 temperature** — CONFIG.md claimed "parsed but not
  currently applied". Actually applied since PR #105 with a
  clamp warning. Rewrote the cell.
- **#13 --api-key** — flag existed but neither README nor
  CONFIG.md mentioned it. Added a Quick-start example noting
  the process-list visibility caveat.
- **#14 acp_host/acp_port** — CONFIG.md documented both keys
  but the CLI flags were intentionally removed (stdio-only
  transport). Removed both from the keys table + ACP section.
- **#6 tools** — `Config::tools` (per-tool enable map) was
  fully wired in code but undocumented. Added a row to the
  keys table covering `tools.websearch` and `tools.webfetch`.
- **#21 find_callers** — README claimed "word-boundary regex"
  but the impl uses the tree-sitter symbol index. Updated to
  reflect actual behavior; the user-visible word-boundary
  semantics are preserved.

## Code

- **#16 semantic index skip_dir** — `SymbolIndex::find_callers`
  filter had its own hardcoded `matches!(name, "node_modules"
  | "target" | ".git" | "__pycache__")` while the rest of
  the codebase uses `agent::tools::is_skip_dir`. Switched to
  the shared helper so future additions stay in lockstep.

- **#18 context::load_file** — silently swallowed
  `read_to_string` errors via `.ok()`. A permission-denied
  AGENTS.md looked identical to a missing file. Now emits a
  stderr warning naming the path + reason; still returns None
  so callers' behavior is unchanged.

725 plugin / 599 default pass. All build profiles clean.

## Remaining audit items (deferred to feature work)

- **#8 LSP no crash restart**: needs broken-pipe IO error
  handling + exponential backoff. Touches manager state
  machine.
- **#10 task tool fire-and-forget**: needs timeout + cleanup
  coordination via JoinHandle tracking.
- **#25 MCP no reconnection**: similar architectural concern
  to #8.
- **#27 LSP didClose**: client lifecycle hook missing.
- **#29 token estimation len/4**: needs per-provider usage
  extraction (Phase 6 work).
- **#5 MCP shutdown**: rmcp Drop semantics need verification.
- **#38/39/40 semantic test gaps**: get_symbol_body untested,
  list_symbols kind_filter untested, find_definition test
  vacuous. Sat down to add but each requires a fixture build.

Together with PR #111 (10 code fixes), 17 of the 23 verified
items are now shipped. Remaining 6 are architectural or
test-infrastructure work better tackled as discrete PRs.

Co-authored-by: Yogthos <yogthos@gmail.com>

…de#112)

Follow-up to PR dirge-code#111. Tier-2 items from the 23-bug audit batch:
docs corrections and two small correctness/UX fixes.

## Docs

- **dirge-code#12 temperature** — CONFIG.md claimed "parsed but not
  currently applied". Actually applied since PR dirge-code#105 with a
  clamp warning. Rewrote the cell.
- **dirge-code#13 --api-key** — flag existed but neither README nor
  CONFIG.md mentioned it. Added a Quick-start example noting
  the process-list visibility caveat.
- **dirge-code#14 acp_host/acp_port** — CONFIG.md documented both keys
  but the CLI flags were intentionally removed (stdio-only
  transport). Removed both from the keys table + ACP section.
- **dirge-code#6 tools** — `Config::tools` (per-tool enable map) was
  fully wired in code but undocumented. Added a row to the
  keys table covering `tools.websearch` and `tools.webfetch`.
- **dirge-code#21 find_callers** — README claimed "word-boundary regex"
  but the impl uses the tree-sitter symbol index. Updated to
  reflect actual behavior; the user-visible word-boundary
  semantics are preserved.

## Code

- **dirge-code#16 semantic index skip_dir** — `SymbolIndex::find_callers`
  filter had its own hardcoded `matches!(name, "node_modules"
  | "target" | ".git" | "__pycache__")` while the rest of
  the codebase uses `agent::tools::is_skip_dir`. Switched to
  the shared helper so future additions stay in lockstep.

- **dirge-code#18 context::load_file** — silently swallowed
  `read_to_string` errors via `.ok()`. A permission-denied
  AGENTS.md looked identical to a missing file. Now emits a
  stderr warning naming the path + reason; still returns None
  so callers' behavior is unchanged.

725 plugin / 599 default pass. All build profiles clean.

## Remaining audit items (deferred to feature work)

- **dirge-code#8 LSP no crash restart**: needs broken-pipe IO error
  handling + exponential backoff. Touches manager state
  machine.
- **dirge-code#10 task tool fire-and-forget**: needs timeout + cleanup
  coordination via JoinHandle tracking.
- **dirge-code#25 MCP no reconnection**: similar architectural concern
  to dirge-code#8.
- **dirge-code#27 LSP didClose**: client lifecycle hook missing.
- **dirge-code#29 token estimation len/4**: needs per-provider usage
  extraction (Phase 6 work).
- **dirge-code#5 MCP shutdown**: rmcp Drop semantics need verification.
- **dirge-code#38/39/40 semantic test gaps**: get_symbol_body untested,
  list_symbols kind_filter untested, find_definition test
  vacuous. Sat down to add but each requires a fixture build.

Together with PR dirge-code#111 (10 code fixes), 17 of the 23 verified
items are now shipped. Remaining 6 are architectural or
test-infrastructure work better tackled as discrete PRs.

Co-authored-by: Yogthos <yogthos@gmail.com>