## Problem
Two session error messages advertised `.claw/sessions/` as the managed-session
location, but the actual on-disk layout is `.claw/sessions/<workspace_fingerprint>/`
where the fingerprint is a 16-char FNV-1a hash of the CWD path.
Users see error messages like:
```
no managed sessions found in .claw/sessions/
```
But the real directory is:
```
.claw/sessions/8497f4bcf995fc19/
```
The error copy was a direct lie — it made workspace-fingerprint partitioning
invisible and left users confused about whether sessions were lost or just in
a different partition.
## Fix
Updated two error formatters to accept the resolved `sessions_root` path
and extract the actual workspace-fingerprint directory:
1. **format_missing_session_reference**: now shows the actual fingerprint dir
and explains that it's a workspace-specific partition
2. **format_no_managed_sessions**: now shows the actual fingerprint dir and
includes a note that sessions from other CWDs are intentionally invisible
Updated all three call sites to pass `&self.sessions_root` to the formatters.
## Examples
**Before:**
```
no managed sessions found in .claw/sessions/
```
**After:**
```
no managed sessions found in .claw/sessions/8497f4bcf995fc19/
Start `claw` to create a session, then rerun with `--resume latest`.
Note: claw partitions sessions per workspace fingerprint; sessions from other CWDs are invisible.
```
```
session not found: nonexistent-id
Hint: managed sessions live in .claw/sessions/8497f4bcf995fc19/ (workspace-specific partition).
Try `latest` for the most recent session or `/session list` in the REPL.
```
## Impact
- Users can now tell from the error message that they're looking in the right
directory (the one their current CWD maps to)
- The workspace-fingerprint partitioning stops being invisible
- Operators understand why sessions from adjacent CWDs don't appear
- Error copy matches the actual on-disk structure
## Tests
All 466 runtime tests pass. Verified on two real workspaces with actual
workspace-fingerprint directories.
Closes ROADMAP #80.
ff45e971aa