UX, diagnostics, install and docs friction (incl. --stats)

Part of #14. Source: v0.10.0 dogfood report (2026-10-07).

Tier: 2

Bugs

#	Sev	Issue	Repro	Expected
B13	M	Tree-sitter warning prints on every default run of the crates.io build (because `--truncate` defaults to `smart`); suggested command is `cargo build --features tree-sitter-all`	`context-builder -d any`	Warn only for explicitly passed flags; suggest `cargo install context-builder --features tree-sitter-all`
B17	L	Errors printed twice, in Debug format, without the path	`-d /nope`; `-o /readonly/x.md` → `Error: Os { code: 13, kind: PermissionDenied, … }`	Print once with `{}`, naming the path; distinct exit codes for cancelled vs IO error (P14)
B18	L	`--max-tokens` notice says `mode: smart` in builds without tree-sitter, but the cut is mid-line	default build, `--max-tokens 50000`	Report the effective mode
B19	L	Malformed or typo'd config silently ignored	`filter = ["rs"` → warning, exit 0, defaults used; `filters = [...]` → no warning	Fail on parse error; warn on unknown keys
B21	L	`--token-count` ignores `--max-tokens`	`--token-count --max-tokens 1000` → 924,288	Report the capped size and files omitted
B23	L	`install.sh` verifies the wrong binary: runs `context-builder --version` from `PATH`, not `$INSTALL_DIR` (printed my cargo copy)	`CONTEXT_BUILDER_INSTALL_DIR=/tmp/x sh install.sh`	Run `"$INSTALL_DIR/context-builder" --version`; warn if not on PATH or shadowed

Enhancements

P7 --stats: per-file token breakdown (--stats / --top 20) that honors --max-tokens and shows what would be cut. Replace the bytes/4 post-run "~NK" estimate (off by −11% to −56%; requests ~1229K vs 2.8M actual) with the real count; the >128K warning should use it too.
P10 discoverability/install: make tree-sitter a default feature (+~10 s compile) or hide the tree-sitter flags when compiled out; add a musl/static Linux release (current binary needs GLIBC_2.34); README says | bash, script header says | sh.
--config <path> / --no-config to bypass a project's context-builder.toml (rest of P8).

Docs / friction (report §6)

Bare context-builder prints help (exit 0). README "Basic Usage" says it processes cwd. Make it process cwd or fix the README.
-o - (stdout) is in the README but not in --help.
Hidden files are skipped and symlinks aren't followed or listed; document it (--hidden is in the v0.11.0 issue; --follow is open).
Absolute paths leak into the header (from the \/tmp/my proj ü/` directory`); use relative paths (P11).
Binary files become <Binary file …> blocks in the body; omit from the body, keep marked in the tree (P11). Ripgrep without .git had 1,095 of these.
Skips and encoding fallbacks go through log::warn!, invisible without RUST_LOG=warn. Env vars (CB_SILENT, CB_DEBUG_CONFIG, CB_DEBUG_AUTODIFF, CB_DIFF_CONTEXT_LINES, RUST_LOG) are only in DEVELOPMENT.md/AGENTS.md.
Diff format (+ /- with a space, ... separator) can't be applied with patch/git apply; state that it's LLM-oriented.

Covers B13, B17, B18, B19, B21, B23 and proposals P7, P10, P14, plus the non-default parts of P8 and P11.

Progress: B13, B17, B18 in #49 (stacked on #44); B23 in #48. Not done: B19 (malformed config / unknown keys; hard-failing is a behavior change, needs a maintainer decision), B21 (--token-count ignoring --max-tokens), --stats/--top, real-tokenizer >128K warning, --config/--no-config, musl release, and the docs/friction checklist items.