fix(mcp): resolve project arg by unique name tail when exact lookup misses

[DeusData]

Closes #1025

Bug

Agents naturally pass the repo folder name (codebase-memory-mcp), but indexed project names derive from the full path (E:\project\graph\x → E-project-graph-x). Every graph tool then answered project not found or not indexed while list_projects clearly showed the project — an unguessable name for any MCP client.

Fix

get_project_arg (the shared getter behind all 11 project-taking tools, same choke point as the #640 aliases) gains a tail-resolution fallback: when no <project>.db exists, scan cache-dir filenames for a segment-aligned tail match (-<project>.db):

• exactly one match → adopt that project's full name (logged as mcp.project_tail_resolved)
• zero or several → keep the original name, so the existing not-found error with the candidate list fires — never guess between projects

Exact names never enter the scan (fast path untouched); internal-name drift stays #704's separate fallback in resolve_store. Filename-level only — no DB opens on the fallback path.

Reproduce-first

tool_project_arg_resolves_unique_tail_issue1025 indexes three real fixtures under an overridden CBM_CACHE_DIR (E-project-graph-suffix1025, F-alpha-amb1025, G-beta-amb1025) and asserts: unique tail suffix1025 resolves (RED on main: project-not-found), ambiguous tail amb1025 stays an error, and the exact full name keeps working.

Verification

Full local suite 6005 passed, 1 skipped, zero regressions; lint-ci clean.