feat: #153 — add post-build binary location and verification guide to README

## Problem

Users frequently ask after building:
- "Where is the claw binary?"
- "Did the build actually work?"
- "Why can't I run \`claw\` from anywhere?"

This happens because \`cargo build\` puts the binary in \`rust/target/debug/claw\`
(or \`rust/target/release/claw\`), and new users don't know:
1. Where to find it
2. How to test it
3. How to add it to PATH (optional but common follow-up)

## Fix

Added new section "Post-build: locate the binary and verify" to README covering:

1. **Binary location table:** debug vs. release, macOS/Linux vs. Windows paths
2. **Verification commands:** Test the binary with \`--help\` and \`doctor\`
3. **Three ways to add to PATH:**
   - Symlink (macOS/Linux): \`ln -s ... /usr/local/bin/claw\`
   - cargo install: \`cargo install --path . --force\`
   - Shell profile update: add rust/target/debug to \$PATH
4. **Troubleshooting:** Common errors ("command not found", "permission denied",
   debug vs. release build speed)

## Impact

New users can now:
- Find the binary immediately after build
- Run it and verify with \`claw doctor\`
- Know their options for system-wide access

Also filed ROADMAP #153 documenting the gap.

Closes ROADMAP #153.

ROADMAP.md

@@ -5905,3 +5905,32 @@ pub fn from_cwd(cwd: impl AsRef<Path>) -> Result<Self, SessionControlError> {
 **Blocker.** None. Implementation exists on worktree `jobdori-127-verb-suffix` but needs rebase against main (conflicts with #141 which already shipped).
 
 **Source.** Clawhip nudge 2026-04-21 21:17 KST — "no excuses, always find something to ship" directive. Session tally: ROADMAP #152.
+
+## Pinpoint #153. README/USAGE missing "add binary to PATH" and "verify install" bridge
+
+**Gap.** After `cargo build --workspace`, new users don't know:
+1. Where the binary actually ends up (e.g., `rust/target/debug/claw` vs. expecting it in `/usr/local/bin`)
+2. How to verify the build succeeded (e.g., `claw --help`, `which claw`, `claw doctor`)
+3. How to add it to PATH for shell integration (optional but common follow-up)
+
+This creates a confusing gap: users build successfully but then get "command not found: claw" and assume the build failed, or they immediately ask "how do I install this properly?"
+
+**Real examples from #claw-code:**
+- "claw not found — did the build fail?"
+- "do I need to `cargo install` this?"
+- "why is the binary at `rust/target/debug/claw` and not just `claw`?"
+
+**Fix shape (~50 lines).** Add a new "Post-build verification and PATH" section in README (after Quick start) covering:
+1. **Where the binary lives:** `rust/target/debug/claw` (debug build) or `rust/target/release/claw` (release)
+2. **Verify it works:** Run `./rust/target/debug/claw --help` and `./rust/target/debug/claw doctor`
+3. **Optional: Add to PATH** — three approaches:
+   - symlink: `ln -s $(pwd)/rust/target/debug/claw /usr/local/bin/claw`
+   - `cargo install --path ./rust` (builds and installs to `~/.cargo/bin/`)
+   - update shell profile to export PATH
+4. **Windows equivalent:** Point to `rust\target\debug\claw.exe` and `cargo install --path .\rust`
+
+**Acceptance:** New users can find the binary location, run it directly, and know their first verification step is `claw doctor`.
+
+**Blocker:** None. Pure documentation.
+
+**Source:** Clawhip nudge 2026-04-21 21:27 KST — onboarding gap from #claw-code observations earlier this month.